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Handbook on Engineering. 



THE PRACTICAL CARE AND MANAGEMENT 



DYNAMOS, MOTdRC^OiWigg.fcNGINES, PUMPS, INSPIRA- 
TORS AND INJIGTORS, ^^pJlGERATING MACHINERY, 
HYDRAULIC fl^E^viTpJS^^LECTRIC ELEVATORS, 
AIR COMPI|eSSQ^^OP| TRANSMISSION AND 
ALL BRANCHES OF STEAM ENGINEERING. 



BY 

HENRY C. TULLEY, 
Engineer and Member Board of Engineers, St. Louis. 



$. 



m 



3^ 



SECOND EDITION. 1902 

Eevised and Enlarged. 



SOLD BY 

HENRY C. TULLEY & CO., 

Wainwright Building, St. Louis, Mo. 

PRICE, $3.50. 






Oif OOP* R«eiii 

lAR 28 |SOS 
oorv fl. 



^ 



Entered according to Act of Congress, in the year 1900, by 

HENRY C. TULLEY, 
In the Office of the Librarian of Congress, at Washington. 





Copyrighted, 1902. 


, '^b^ 




•;-•;•;::;: < 


^yy^.y-j i 


Nixon-Jones Printing Co 

215 Pink Street, 

St. Louis. 





INTRODUCTION. 

The object of the writer in preparing this work has been to 
present to the practical engineer a book to which he can, with 
confidence, refer to for information regarding every branch of 
his profession. 

Up to the date of the i3iiblication of this book, it was impossi- 
ble to find a plain and practical treatise on the steam boiler, steam 
pump, steam engine, and dynamo, and how to care for them; 
electric and hydraulic elevators, and how to care for them ; and 
all other work that an engineer is apt to come in contact with in 
his profession. 

An experience of over twenty-five years with all kinds of en- 
gines and boilers, pumps, and all other kinds of machinery, ena- 
bles the writer to fully understand the kind of information most 
needed by men having charge of steam engines of every descrip- 
tion, and what they should comj^rehend and employ. 

With this object in view, the writer has carefully made note of 
his past experience, and has also made note of things that came 
to his notice while visiting different engine rooms, and accord- 
ingly, has taken up each subject singly, excluding therefrom, 
everything not strictly connected with steam engineering. 

Particular attention has been given to the latest improvements 
in all classes of steam engineering and their proportioning, ac- 
cording to the best modern practice, which, it is hoped, will be 
of great value to engineers, as nothing of the kind has heretofore 
been published. 

This book also contains ample instructions for setting up, lining, 
reversing and setting the valves of all classes of engines. 

'^HE AUTHOR. 

:iii) 



PAGE 



I CONTENTS. 

CHAPTER I. 
The Elementary Principles of Electrical Machinery , . . 1 

CHAPTER II. 
The Principles of Electromagnetic Induction c . , , . 14 

CHAPTER III. 

Two-Pole Generators and Motors . . c . . . . . 27 

CHAPTER IV. 

Multipolar Machines ...,,., 38 

CHAPTER V. 

Switch Board, Distributing Circuits, and Switch Board 
.:, Instruments ....,....,,... 47 

" CHAPTER VI. 

Electric Motors 64 

CHAPTER VII. 

Instructions for Installing and Operating Slow and Moder- 
ate Speed Generators and Motors 74 

CHAPTER VIII. 

Why Commutator Brushes Spark and Why They Do Not 

Spark ..,„..... 80 

(V) 



VI CONTENTS. 

CHAPTER IX 

PAGE 

Instructions for Installing and Operating Apparatus for Arc 

Lighting Brush System 117 

CHAPTER X. 
Installation of Arc Dynamos, T. H. System 168 

CHAPTER XI. 
The Steam Engine 210 

CHAPTER XII. 

The Steam Engine — Continued . . . 237 

CHAPTER XIII. 

Taking Charge of a Steam Power Plant 323 

CHAPTER XIV. 

A Few Remarks on the Indicator 345 . 

CHAPTER XV . 

Economy of Steam Engines . 380 

CHAPTER XVI. 

The Steam Boiler . 398 

CHAPTER XVII. 

Use and Abuse of the Steam Boiler 449 

CHAPTER XVIII. 

The Water Tube Sectional Boiler 502 : 



CONTENTS. Vll 

CHAPTER XIX. 

PA.GE 

The Steam Pump 544 

CHAPTER XX. 

The Injector and Inspirator 591 

CHAPTER XXI. 

Mechanical Refrigeration 519 

CHAPTER XXII. 

Some Practical Questions Usually Asked of Engineers 
When Applying for License 646 

CHAPTER XXIII. 

Instructions for Lining Up Extension to Line Shaft . . 672 

CHAPTER XXIV. 

Horse Power of Gears 695 

CHAPTER XXV. 

Electric Elevators . . . . . 716 

CHAPTER XXVI. 

Hydraulic Elevators 766 

CHAPTER XXVII. 

The Driving Power of Belts 788 

CHAPTER XXVIII. 

Air Compressors, The Metric System, Thermometers, 

Rope Transmission 800 



HANDBOOK ON ENGINEERING. 



CHAPTER I. 



THE ELEMENTARY PRINCIPLES OF ELECTRICAL 
MACHINERY. 

The operation of electric generators, or dynamos, as they are 
ordinarily called, and also that of electric motors, depends upon 
a simple relation between electricity and magnetism, which will 
be explained in a simple manner in the following paragraphs. 



JV 



JV 



Fm. 1. 




Fig 



Fig. 4. 



(f 




lU 



Fig 



A permanent magnet, as is well known, is a bar of steel which 
possesses the power of attracting pieces of iron. These bars may 
be made straight,- as in Fig. 1, or in the form of a U, as in Fig. 
2, or in any other shape desired. The strength of a permanent 
magnet depends upon the kind of steel of which it is made, and 

1 



2 HANDBOOK ON ENGINEERING. 

also upon the temper it is given. Generally speaking, the harder 
the steel the stronger the magnet. A bar of soft steel, or wrought 
iron, cannot be made into a permanent magnet of any noticeable 
strength, but if such a bar is covered with a coil of wire, as shown 
in Figs. 3 and 4, and a current of electricity is passed through 
the wire, the bar will be converted into a very strong magnet so 
long as the current flows. As soon as the electric current stops 
flowing through the wire, the magnetism of the bar will die out. 

Magnets of the last-named type are called electro-magnets, as 
they do not possess magnet properties except when the electric 
current flows around them. Electro-magnets, when energized by 
sufficiently strong electric currents, can be far more powerful than 
the permanent magnets, and on that account they are used in 
electric generators and motors. In addition to being stronger 
magnets, the electro-rnagnet has the advantage that it can be 
magnetized and demagnetized almost instantly, by simply cutting 
off the exciting electric current, and on this account they can be 
used for parts of electrical machines and apparatus, for which the 
permanent magnet would be entirely unsuited. 

If we test the attractive power of a magnet, we will find that 
it is greatest at the ends, the force at the middle point being 
scarcely noticeable. A bar such as Fig. 1 or Fig. 3 might hold a 
piece of iron weighing several pounds, if presented to either end, 
while at the middle point, it might not be able to sustain more 
than an ounce or two. Owing to this fact, the ends are called 
the poles of the magnet. 

If any magnet is suspended from its center, like a scale beam, 
and allowed to swing freely, it will be found that it v/ill come to 
rest in a north and south jDosition, and no matter how violently it 
may be moved around, it will always come to a state of rest 
with the same end pointing towards the north. On this ac- 
count, the ends are called north and south poles, the north pole 
being the end that points toward the north. 



HANDBOOK ON ENGINEERING. 6 

If two-bar magnets are suspended side by side with thie 
north end of one at the top and the north end of the other 
at the bottom, as is ilhistrated in Fig. 5, thej will attract each 
other; but if both magnets had the north end at the top, they 
will push away, as shown in Fig. 6. It is evident that there is 
a good reason for this difference in action, and this reason we 
can find out by experiment. 




^ JV 



Fio^. 5. 




A magnet needle, such as is used in mariner's compasses, is 
simply a small magnet. If we place a magnet bar, as shown in 
Fig. 7, and then set near to it, in different positions, a compass 
containing a very small needle, we will find that in these several 
positions the direction of the needle will be about as is indicated 
by the small arrows marked h on the curved lines a a; the point 
of the arrow being the north end, or pole of the needle. The 
reason why the needle will take up these positions is that the north 
end of the bar attracts the south end of the needle, and pushes 
away the north end, just as in Figs. 5 and 6, and the south end 
of the bar acts in the same way ; so that there is a tug of war 
going on, so to speak, between the attractions and repulsions of 



4 HANDBOOK ON ENGINEERING. 

the two ends of the bar upon the two ends of the needle, the 
result being that the position assumed by the needle is the re- 
sultant of these several actions. When the needle is near the 



y'"^- 



\ 



^ y 

"^..v^ 



^ 



a\ 



V 



a' 



Fiaf. 7. 






nj.'ifi 















Fig. 



north pole of the bar, its south end is attracted with the greatest 
force, and when near the south end of the bar, the north end ex- 
periences the greatest attraction. 

If we were to place the exploring needle in all possible posi- 
tions near the magnet and trace lines parallel with it, in these 
positions, we would obtain a large number of curves about the 
shape of those shown in Fig. 8. As these curves represent the 
direction into which the magnet needle is turned at the various 
points in the vicinity of the magnet, they represent the direction 
in which the combined forces of the two poles act at these two 
points, hence, these lines are called magnetic lines of force. 



HANDBOOK ON ENGINEERING. 

When two ma§;nets are suspended as iii Fig. 5, the lines of 
force of botti will be in the same direction as is indicated in Fig. 
9 by the arrow heads on the curves a a. That this is true can be 
seen from Fig. 7, in which it will be seen that the arrow heads 
point toward the south pole and away from the north pole. 
As the north pole of a magnet has an attraction for the south 
pole, we can readily see that there is an endwise pull in the 
lines of force, which tends to make them contract, like rubber 
bands, hence, we can imagine the lines a a in Fig. 9 to contract 
and thus draw the two magnet bars together. 

The repulsion of the two magnets, when the north poles are at 
the same end, is illustrated in Fig. 10. Here we see that the lines 
of force passing on the outside of the bars, as indicated by 
lines a a, are unobstructed, and can assume their natural posi- 



a 



JV 



J^ 



Fio-. 9. 




Fiff. 10. 



tion, but those that pass between the bars, along line c, are 
pressed out of position. If we assume that the lines of force 
make an effort to retain their position, like so many wire 



h TIANDBOOK ON ENGINEKRING. 

spriugs, then wc ciiu sec tliiit the repulsion is due to the effort that 
the lines make to assume their natural form in the space between 
the bars. 

Magnetic lines of force have no real existence, they simply in- 
dicate the direction in which the force acts, but if we keep this 
fact in mind, it helps us to understand magnetic actions, if we 
treat the lines of force as if they were something real. This fact 
will become more evident as we proceed. 

Lines of force always pass from the north to the south pole 
through the space between these poles, and through the magnet 
itself, they are assumed to pass from the south to the north pole. 
The form of the lines of force depends upon the relative position 
of the north and south poles. In Fig. 9 they are curved, as 



J^^^MS j\r 



Fig. 11. 

the magnets are placed side by side, but if the bars were arranged 
end to end, as in Fig. 11, the lines of force would be straight, as 
is shown at a. From the north end of the right side magnet, the 
lines of force would pass in curved line, as in Fig. 10, to the south 
pole of the magnet on the left side, thus completing the magnetic 
chain, or circuit, as it is called. 

If we take the two magnet bars of Fig. 11 and stand them on 
end, as in Fig. 12, and suspend a bent wire C in the manner 
shown, effects can be produced that are interesting and instruct- 
ive, as they illustrate the principle upon which generators and 
motors act. The wire C should be journaled at D D, so as to 
swing with as little friction as jjossible, and its ends are to be con- 
nected with a battery JS, by means of fine wires a and 6; a switch 
being provided at e so as to stop the flow of current when desired. 



HANDBOOK ON ENGINEERING » 7 

I* the switch c is opened, so tliatno current flows tlirough C, the 
latter will not be disturbed, and if we give it a swing, it will oscil- 
late back and forth, like a clock pendulum, and in a few seconds 
come to rest in the position in which it is shown^ If the switch 
is closed, C will at once swing out of the stream of magnetic lines 
of force and will remain in that position as long as the current 
from the battery passes through it. The direction in which C 




will swing will depend upon the direction of the current through 
it. If with the wires a and b connected with the battery, in the 
manner shown, the wire swings to the right side, then if a is 
connected with e, and h with d, the direction of swing will be 
reversed ; that is, C will swing toward the left. 

From this experiment we see that the magnetic lines of force 
can develop a repulsive force against an electric current, and that 
the direction of the repulsion depends upon the direction of the 



HANDBOOK ON ENGINEERING. 



electric current with respect to the direction ol' the hnes of force. 
We now desire to know wh}^ this repulsion is developed, and this 
we can ascertain by the following experiments : — 

If we arrange three wires as shown in Figs. 13, 14 and 15, so 
as to run north and south, the upper end being north, and place 
over these magnet needles D D D, pivoted at e e e, we will find 
that if there is no current flowing through the Avire, the needle 
will point toward the north, or be parallel with the wire, as is 



B 





Fig. 14. 



Fi^. 15. 



shown in Fig. 14. If the current runs through the wire from 
south to north, the north end of the needle will swing to the right, 
as in Fig. 15, and if the current runs through the wire from north 
to south, the north end of the needle will swing toward the left, 
as in Fig. 13. From this we see that an electric current can 
repel a magnet, and that the direction in which it repels it depends 
upon the direction of the current. 

If we stand the three wires on end, as shown in Figs. 16, 17 
and 18, in which A B C represent the wires as seen from above, 
we will find out more about the relation between electric currents 



HANDBOOK ON ENGINEERING. 



9 



and magnets. If we i^lacefoiir small magnet needles around eaeh 
one of the wires, as shown at a a a «, we will find that those 
around the center wire, through which no current flows, will all 



/" 



a 






a 



/ 



\ ® «| {- ® «j \^ m a| 



Fig. Ifi, 



Fior. 17 



Fiff. 18. 



point toward the north, as shown, while those around the wire 
Fig. 16, through which a current flows upward, that is, away from 
the center of the earth, will point in a direction opposite to that 
in which the hands of a clock move; and in wire Fig. 18, in 
which the electric current flows down toward the center of the 
earth, the north ends of all the needles will point in the direction 
in which the hands of a clock move, that is, just opposite to those 
in Fig. 16. 





Fig. 20. 

From these actions, we infer at once that when an electric 
current flows through a wire, the latter becomes surrounded 
with magnetic lines of force, as is illustrated in Figs. 19 and 20, 



10 HANDBOOK ON P^NGINEERING . 

and that there is a lixed relation between the direction of the 
current and that of the lines of force. At A, Fig. 19, the direc- 
tion of the lines of force is shown for a current moving up- 
ward, and at B, Fig. 20, the direction of the lines of force is 
that due to a curi^ent moving downward through the wire. 

Inasmuch as an electric current flowing through a wire is 
surrounded by magnetic lines of force, we can say that a com- 
plete electric current consists of two parts, one the current proper, 
which traverses the wire, and the other the magnetic casing which 
envelops the wire. It is the action between the latter part of the 
current and the lines of force of magnets that develops the 
current in a generator, or the power in a motor. 

With the aid of Figs. 21 and 22, we can now show how the 
force is developed that thrusts the wire to one side in Fig. 12. 
The lines of force of the magnet, which constitute what is called 
the magnetic field, will flow from the north pole at the top to the 
south pole at the bottom, as is shown in Figs. 21 and 22. If the 
electric current flows through the wire C from the back toward 
the front, the lines of force developed around it will have the 
direction shown in Fig. 21. As lines of force cannot flow in op- 
posite directions in the same space, the lines of the field will swing 
over to the left side of the wire, but in doing so they will be 
stretched out of the straight form, and they will also push the 
lines surrounding the wire out of their central position. Under 
these conditions, which are illustrated in Fig. 21, the effort made 
by the field lines to straighten out, together with the effort made 
by the wire lines to return to the central position, will develop a 
thrust between the wire and the field, and thus force the former 
out toward the right side. 

If the direction of the current through the wire is reversed so 
as to flow from front to back, the direction of the lines of force 
around the wire will be reversed, and will be as in Fig. 22. Under 
these conditions, the lines of force of the magnetic field will 



HANDBOOK ON ENGINEERING, 



11 



swing over to the right .side of the wire, tiiid thus the thrust will 
be in the opposite direction. 

Fig, 12 represents the principle of an electric motor in its sim- 
plest form, and from it we see that the force that causes the 
armature to rotate is developed by the repulsion between the mag- 
netism of the field magnet and the magnetism that surrounds the 
wires wound upon the armature. 










■vv^^: 



Fig. 21. 




It is self-evident that if we undertake to force the wire C 
through the magnetic field in the opposite direction to that in 
which it swings, we will have to make an effort to do so ; that is, 
if we try to move the wire from right to left in Fig. 21, or from 
left to right in Fig. 22, we will have to apply power. Now nature 
is a strict accountant and does not allow any power to be lost ; 
therefore, all the energy we expend in moving the wire through 
the magnetic field must appear in some other form, and the form 
in which it appears is as an electric current that is generated in 



12 HANDBOOK ON ENGINEERING. 

the wire. If we were to reinoA^e the battery in Fig. 12 and put 
in its place an instrument to indicate the presence of a current in 
the wire, we would find that when we move the latter in the 
opposite direction to that in which it moves under the influence of 
the current, we generate a current; that is, we convert the device 
into a simple electric generator. If in Fig. 21, we move the wire 
from right to left, the direction of the current generated in the 
wire will be the same as that of the current which causes the wire 
to swing in the opposite direction, that is, from back toward the 
front. As it is a poor rule that does not work both ways, we 
would naturally infer that if moving the wire from right to left 
develops a current from back to front, movement in the opposite 
direction would develop a current from front to back ; and such 
is actually the case. This fact can be demonstrated by Fig. 12. 
Suppose that in this figure we hold C stationary in the central 
position, and then pass a current through from back toward the 
front ; this current would exert a force to swing C to the right 
side. If we release the wire, it will swing to the right and as 
soon as it begins to move, the current will become weaker, show- 
ing that the movement of the wire developed therein a current in 
the opposite direction. If we force the wire over to the left side, 
the current flowing through it will begin to increase as soon as 
the wire moves. 

All the foregoing shows us that when a wire is moved through 
a magnetic field, a current will be generated in it if it forms part 
of a closed circuit, and it makes no difference whether there is a 
current already flowing in the wire or not. When the wire is 
caused to move through the magnetic field by a current flowing 
through it from an external source, the current developed in it will 
be in opposition to that which comes from the external source, 
and, as a consequence, the movement produces an actual reduc- 
tion of the strength of current flowing through the wire. The 
stronger the magnetic field and the greater the velocity of the 



HANDBOOK ON ENGINEERING. I'd 

wire, the stronger the current generated in opposition to the driv- 
ing current, and, therefore, the weaker the latter. It is on this 
account that if a motor is allowed to run free, the faster it runs 
the weaker the current through it becomes, as the actual current 
in every case can only be the difference between the main driving 
current and the one developed in the wire, which latter runs in 
the opposite direction. 

Magfnetic force is measured in units that are based upon the 
centimeter grame second system which is too technical to be ex- 
plained in a few words. Briefly stated a unit of magnetic force 
will exert a pull of unit mechanical force at a unit distance. 

The force of magnets is measured either by the total force of 
the magnet, or by the force exerted by each unit of cross-section. 
When the measurement is based upon the total force of the mag- 
net, the unit is called a Maxwell ; thus we speak of the total flux 
of a magnet as so many maxwells. When the measurement is 
referred to the force per unit of cross-section, it is spoken of as 
the magnetic density, or density of magnetization, and the unit 
used is called a Gauss ; thus we speak of a magnet as having a 
density of so many gausses per square centimeter, or square 
inch of cross-section. The density of magnetization is deter- 
mined by a rule given on page 46. 

The lifting- capacity of a magnet can be determined by the 
following rule : — 

TO FIND THE LIFTING CAPACITY OF A MAGNET IN POUNDS. 

Multiply the area of cross-section of the magnet pole in square 
inches, by the square of the density of magnetization per square 
inch, and divide this product by 72 millions. 

This rule gives the pull for one pole. For horse shoe magnets 
double the figures. If the object lifted is not in contact with 
\M? poles the pull will be less than rule gives. 



14 HANDBOOK ON ENGINEERING 



CHAPTER II. 
THE PRINCIPLES OF ELECTROMAGNETIC INDUCTION. 

By Electromagnetic Induction, I mean the inductiou of electric 
currents by magnetic action. In the preceding chapter it has been 
shown that if we move a wire through a magnetic field, an electric 
current will be generated in it, providing its ends are joined, so 
as to form a closed circuit. If the ends are not joined, then there 
will be no current developed, because, an electric current cannot 
flow except in a closed circuit. When the ends of the wire are 
not joined, the movement through the field develops simply an 
electromotive force. Electromotive force is that force which 
causes an electric current to flow when there is a circuit in which 
it can flow. Electromotive force is a long-winded name and on 
that account it is always abbreviated into e.m.f., so that here- 
after when these letters are used, it will be understood that they 
stand for electromotive force. 

Metals and all other substances that allow electric currents 
to flow through them are called conductors, while glass, mica, 
wood, paper and many other similar forms of matter that do not 
allow currents to flow through them are called insulators. The 
difference between conductors and insulators is only one of 
degree, for there is no known substance that is an absolute non- 
conductor of electricity ; that is, a perfect insulator ; and there is 
no substance that does not resist to some extent the passage of a 
current — that is, there is no such thing as a perfect conductor. 
Some substances, like damp paper or wood, which stand midway 
between good conductors and good insulators, can be regarded as 
either one or the other, depending u^jon the service for which they 
are used. For currents of very low e.m.f., they would be in- 



HANDBOOK ON ENGINEERING. 15 

sulators, but for currents of very high e.m.f., they would be 
conductors. 

The current that will flow through any circuit when impelled 
by an e.m.f., will have a strength that will depend upon the 
amount of resistance that opposes its flow. As all conducting 
materials are not of the same degree of conductivity, their relative 
values are determined by the amount of resistance they interpose 
to the flow of the current. The resistance of a conductor is 
measured in units called ohms ; the strength of current is 
measured in units called amperes, and the e.m.f. is measured in 
units called volts. The relation between these units is such that 
an e.m.f. of one volt will cause a current of one ampere to flow 
in a circuit having a resistance of one ohm. 

When a wire is moved through a magnetic field, the e.m.f. 
induced in it will be determined by the strength of the field and 
the velocity with which the wire moves, and will not be affected 
in any way by the resistance of the circuit of which the wire 
forms a part. If the resistance is very great, the strength of 
current generated will be very low, and if the resistance is very 
low the current will be strong, but in either case the e.m.f. will 
be the same. 

If movement of the wire in one direction develops an e.m.f. 
in a given direction through the circuit, then movement of the 
wire in opposite direction will reverse the direction of the e.m.f. 
Thus, in Fig. 23, which represents a magnetic field between 
the poles N' S, if wire a is moved from right to left, it will have 
induced in it an e.m.f. that will be from back to front, and if 
the direction of motion of the wire is reversed, the e.m.f. will 
also be reversed. This will be true whether the wire is near the 
-A^pole or /S' pole. This being the case, it can be seen that if 
a represents the end of a wire moving in the direction of arrow 
d, and b the end of a wire moving in the opposite direction, the 
e.m.f. 'sin these two wires will be in opposite directions. The 



16 



HANDBOOK ON ENGINEERINC4. 



direction of the e.m.f. in a will be up from the paper toward 
the observer, and the direction of the e.m.f. in h will be down 
through the paper. If these two wires are secured to a shaft 
placed in the center of the field, then by the continuous rotation 





Fig. 23. 



Fig. 24. 



of the shaft, the two wires can be made to revolve around the 
circular path shown. 

If these two wires are joined at the ends, as shown in Fig. 24, 
they will form a closed loop, and although the direction of the 
induced e.m.f. in the two sides will be opposite, when compared 
to a fixed point in space, they will be in the same direction so 
far as the loop is concerned ; that is, both e.m.f. 's will develop 
currents that will flow through the wire in the same directions. 

Returning to Fig- 23 it will be noticed that if the wires re- 
volve around the circular path at a uniform velocity, their move- 
ment in the direction of line c c will not be uniform, but will be 
the greatest when the wires are in the position shown, and least, 
when they cross the hue c c. In fact, when the wires cross line 
c c their motion in the direction of this line will be zero, for this 



HANDBOOK ON ENGINEP^RING . 



17 



is the point where the direction of movement reverses. Now, 
the magnitude of the e.m.f. induced in the wire is proportional 
to the velocity in the direction of the line c c, hence, when the 
wires are crossing this line, the e.m.f. will be zero, and when 
they are one-quarter of a turn ahead of the line, the e.m.f. will 
be the highest. 

In Fi§:. 24 we see that in side a, the direction of the current 
is toward the front, and in b it is the reverse ; now, when a 
moves through half a turn, it will take the place of b, and the 
direction of the e.m.f. induced in it will be the same as in b in 
the figure ; that is, it will be the reverse of what it is when pass- 
ing in front of the pole N. This being the case, it is evident 
that each time the loop makes a half -re volution, the direction of 
the current generated in it reverses. ; 



/ 


A 


— 


r 


A 








// 


/ 


■ ^9- 






JT- /-/- 


-7/ 


>// 






/,./ 


j/i 








VJi 




'~l 


^ 7^ 7^ 


VI 


K 


-A 




u 


4- 




Ml 






, 1 




—/ 


^S\ • 


"4 




^ 


'~-~«r^^' \\ 


i 




TM^ VSr 


/ 


w\^^ 




_>^ . 


Fig. 25. 







As the loop in Fig. 24 is closed, the current generated in it 

would be of no practical value, but if we cut the wire at one 

side and connects the ends with rings as shown at a and b in Fig. 

25, then by means of collecting brushes c c we can take the cur- 

2 



18 



HANDBOOK ON ENGINEERING. 



rent off through the wires d d. This current, however, would 
consist of a series of impulses that would flow in opposite direc- 
tions, each one starting from nothing and increasing to its greatest 




Fig. 26. 



strength when the loop reaches the position shown in the figure, 
and then declining and reaching the zero value when the loop 
reaches the vertical position. Such a current is called an alter- 
nating current, because it flows first in one direction and tlien in 
the opi30site direction. All forms of machines that generate cur- 
rents by electromagnetic induction, develop alternating currents, 
but in the class of machines known as direct or continuous current, 
a rectifying device is used which rectifies the current before it 
reaches the external circuit. This rectifying device is called a 
commutator, and is illustrated in its simplest form in Fig 26. In 
this illustration it will be noticed that the ends of the wire, instead 
of being attached to two independent rings, placed side by side, 
are secured to two half-rings, placed opposite each other. The 
brushes c d, through which the current is taken off, are held 
station ar}" ; therefore, as can l)e readily seen, c will make contact 



HANDBOOK ON ENC4rNEERING. 19 

with a during oue-half of the revolutiou, and with b during the 
other half ; and this will also be the case with brush d. Now, as 
the half-rings with which the brushes are in contact change at 
each half revolution, it follows that by properly setting the 
brushes, they can be made to pass from one-half ring to the other 
at the very instant when the direction of the current in the loop 
reverses, so that through each brush there will be a succession of 
current impulses, but all in the same direction. 

The device shown in Fig. 25 is a perfect alternating current 
generator, and that shown in Fig. 26 is a perfect direct current 
generator. In both cases, however, the e.m.f. induced is so 
low as to be of no practical value. To obtain serviceable 
machines, capable of developing the e.m.f. and current strength 
required in practice, it is necessary to provide very strong mag- 
netic fields and to rotate in these a large number of loops of wire. 
In order that the operation of such machines may be understood, 
I will first show how the powerful magnetic fields are obtained. 

In Fig. 27 two wires are shown as seen from the end, these 
being marked A and J5. The lines of force surrounding them are 

^ — -^\^ // - 



N^. 



sm^ 






Fig. 28. Fig. 27. 

in directions that correspond to opposite directions of current in 
the wires. In wire ^1, the current flows away from the observer. 
As can be seen, the lines of force of both wires have to crowd into 



20 HANDBOOK OX ENGINEERING. 

the space between the wires, for on the outside of A the two sets 
of lines would meet each other head on, and this would also be 
the case on the right side of wire B. This crowding of the lines 
of force into the space between the wires causes them to distort 
from their natural position and instead of being central with the 
wires, are eccentric to them. If we take a long wire through 
which a current is flowing and bend it into a loop, we will see 
that if the current flows out through one side, it will return 
through the other side, so that in the two sides of the loop the 
current will flow in opposite directions. This being the case. 
Fig. 27 can be regarded as showing the two sides of such a loop, 
and from it we find that the effect of such a loop is to concentrate 
within its interior nearly all the lines of force that surround the 
wire. 

In Fig* 28 the two wires A and B are surrounded with lines 
of force that correspond to the same direction of current. In 
this case it will be noticed that in the space between the wires the 
lines of force flow in opposite directions ; hence, only a few of the 
lines will follow this path, simply that number surrounding each 
wire that can traverse the space without encroaching upon the 
path of the lines belonging to the other wire. If the two wires 
are very near to each other, practically all the lines of force of 
both wires will join forces, so to speak, and pass around the two 
wires. Now, if we wind a wire into a coil of many turns, the 
direction of the current in the several turns will be the same, so 
that the lines of force of all the turns will combine into one large 
stream and circulate around the entire coil side, no matter how 
many turns of wire it may contain. From this it can be seen 
that if we have a current of say ten amperes, we can make it 
produce just as powerful magnetic effect as a current of one 
thousand amperes, by simply increasing the number of turns of 
wire in the coil. A (;urrent of ten amperes passing through a coil 
of wire containing one hundred turns, will have the same magnet- 



HANDBOOK ON P:NC4TNEER1NG . 



21 



ism in effect, as a current of one hundred amperes passing tlirougli 
a coil of ten turns, or as a current of one thousand amperes pass- 
ing through a coil of a single turn. 

If we place at the side of a wire through which an electric 
current is flowing a piece of iron, as is shown in Fig. 29, the 
effect will be that the lines of force will no longer flow in circular 
paths, as indicated by the circle a, but will be deflected in the 
manner illustrated, by the presence of the iron. If, instead of 






/ 



al 









Fio-. 29. 



7'/ ^ ' 
/ / 




Fig. 30. 



the straight iron bar, we substitute a ring of iron, as in Fig. 30, 
nearly all the lines of force will be concentrated in the metal, and 
the magnetic field in the space 0, between the ends of the ring, 
will be vastly greater than at any other point. The explanation 
of these actions is .that all forms of matter oppose the develop- 
ment of magnetic force, but some offer greater resistance than 
others. Iron, steel, nickel, and one or two other metals, offer 
less resistance to the magnetic lines of force than air, and are 
said to have a higher magnetic permeability. Nickel is only a 
slight improvement on air, but steel and iron are far superior, 
iron being of about two to three times the permeability of hard- 



22 



HANDBOOK OX ENGINEERING. 



died steel, and about one thousand times the permeability of air, 
when magnetized to the density ordinarily used in practice. The 
iron in Figs. 29 and 30, therefore, becomes the path of the lines 
of force, because it interposes a much lower resistance. O wing- 
to this difference in the resistance of iron and air, it is possible 
to make an iron magnet core of any desired form, and to con- 
centrate within it nearly all the lines of force developed by the 
current flowing through the wire wound upon it. The presence 
of the iron not only serves to concentrate the magnetism in it, 
but as it reduces the resistance opposing the development of 
the magnetism, it enables the field to be made vastly stronger 
than it could be with air alone, say a thousand times as great. 

If we make a magnet in the form of Fig. 31, with a coil of 
wire around the partB, practically all the lines of force will flow to 




the poles N S, and will pass through the air space between them. 
If this air space is nearly filled with a cylindrical mass of iron, A^ 
the strength of the magnet will be increased, for, by doing this, 



HANDBOOK ON ENGINEERING. 



23 



we replace air which is a poor magnetic conductor, by iron which 
is a far superior conductor. Electric motors and generators are 
made with a cylindrical mass of iron at A, which is the armature 





Fio;. 32. 



Fig-. 33. 



core, and the air space between it and the faces of the poles of the 
field magnet is made just sufficient to accommodate the wire 
coils, and by this means the field strength is increased as much as 
jjossible. 

The armatufe cores are sometimes made solid, as in Fig. 32, 
and sometimes as a ring, as in Fig. 33. When they are solid, 
the lines of force cross through them in straight lines, see Fig. 
32 ; and when they are ring form, the lines follow the ring and do 
not penetrate the interior space. 

If the single loop of Fig. 24 is replaced by a coil containing 
many turns of wire, the e.m.f. induced in it will be increased in 
proportion with the number of turns of wire in the coil, so that by 
using such a coil in a field such as shown in Fig. 31, a high 
e.m.f. can be obtained. This e.m.f., however, would be alter- 
nating, and if the current were rectified by means of a commu- 



24 



HANDBOOK ON ENGINEERING. 



tator, it would not be of uniform strength, but would fluctuate 
from a maximum value to zero. Just how the current would 
fluctuate and how the construction can be changed so as to get rid 
of the fluctuation, we can explain by presenting a diagram that 
illustrates the alternating current as it flows in the armature coil, 
and the rectified current as it leaves the commutator. 

In Fig', 34^ let the distance /' li, 7i i, i n, along the line// 
represent half -revolutions of the coil, and let distances measured 
on the vertical line c d represent the strength of current, distances 
above/ being current flowing in one direction, and distances below 
/being for current flowing in the opposite direction. Let us con- 
sider the instant when the coil is passing the point where the 
e.m.f. induced is zero; then this instant will be represented 
by the point /, at the left of the diagram, and the curve a 
will start from this i)oint ; as at that instant, the current which it 
represents has no value. As the coil rotates, the current begins 
to grow, and this fact we indicate by causing curve a to gradually 



Fig. 34. f 



Fig. 35 




rise above the horizontal line. At the quarter turn, the current 
reaches its greatest strength, thus this forms the highest point of 
curve «, and is midway between / and h. From this point 



HANDBOOK ON ENGINEERING. 



25 



onward, the current declines and becomes zero, when the rotation 
of the coil has reached one-half of a revolution, which is repre- 
sented by the point h. In the next half -revolution, the current 





Fi^. 36. 



Fi^. 38. 



flows in the reverse direction, but has the same maximum strength 
and increases and decreases at the same rate; therefore, the curve 
h^ drawn below the horizontal line, represents the reverse current ; 
and point i corresponds to one complete revolution, so that 
beyond i the curves a and h are repeated in systematic order. 

NoWy if we provide a commutator to rectify this current, all 
we can accomijlish is to turn curve h upside down and transfer it 
to the upper side of the horizontal line, as in Fig. 35 ; but, as 
will be seen, all we accomplish by this act is to obtain a current 
that flows always in the same direction, but at each half-revo- 
lution it drops down to a zero value. 

If we wind two coils upon the armature, placing them at right 
angles with each other, as is indicated by A and B in Fig. 36, 
then if the currents of these two coils are rectified, they will bear 
the relation toward each other shown at the upper line in Fig. 37, 
the a a curves in solid lines representing the- current from the A 
coil, and the 5 h curves in broken lines, representing the current 
from the B coil. As will be seen, when one of these currents is 
zero, the other is at its greatest value, so that if we run both into 



2i^ 



HANDBOOK ON ENGINEERINC4. 



the same circuit, tlie lowest value of the combined current would 
be equal to the maximum of either one of the single currents, 
and the maximum value would be equal to the sum of the two 
currents when the coils are on the eio^hths of the revolution. 




Fig. 37. 



This resulting current is shown on the lower line in Fig. 37 by 
the curve cl d. From this curve we see that the number of 
fluctuations in the current has been doubled, but the variation in 
the .strength is greatly reduced. If w^e wound four coils upon 
the armature, as indicated hj A B C D, in Fig. 38, the number 
of undulations in the combined current would be again doubled, 
but the fluctuation would be very much less. If the number of 
coils is increased to twenty-five or thirty, the fluctuations in the 
current become so small as to be hardly worth noticing. 

With coils such as shown in Fig. 26, a separate commutator 
would have to be provided for each coil, and this would render 
the machine very complicated, if the number of coils were even 
six or eight; hence, in actual machines, the winding of the coils 
is modified so as to be able to use a single commutator for any 
number of coils. This construction will be explained in the 
next chajDter. 



HANDBOOK ON ENGINEERING. 



27 



CHAPTER III. 

TWO POLE GENERATORS AND MOTORS. 

The simplest type of armature winding is that used with ring 
cores, and is illustrated in Fig. 39. As will be seen, it is simply 
a continuous winding all the way around the circle, the end of 
the last turn of wire being connected with the beginning of the 
first turn, so as to form an endless coil. If wires are attached at 
a and 5, and a current is passed through, it will divide into two 
halves, one part flowing through the wire above a &, and the other 
part through the wire below a b. In the upper half of the wire, 
the direction of the current in the front sides of the turns will be 
toward the center of the ring, as is indicated by the arrow heads, 
and in the lower half it will be away from the center. If, in- 




stead of attaching wires at a and b we place stationary springs, so 
as to press against the wire, then we could revolve the ring, and 
still the current would enter and leave the wire at the same points. 
Small armatures are often made in this way, but for regular 



28 HANDBOOK ON ENGINEERING. 

machines it is more desirable to provide a commutator as shown 
in Fig. 40 at C, and then the several segments can be connected 
with the wire at regular intervals. In the figure, the commutator 
is provided with twelve segments, and these connect with the 
armature wire at every fourth turn, so that the wire is divided 
into twelve coils of four turns each. 

The only difference between this diagram and a regular gen- 
erator armature of the ring type, is that it show^s the wire coils 
spread out with a considerable space between them, and only in 
one layer, while in the actual machine, the wire is wound close 
together and generally, in several layers; but no matter how many 
layers there may be, or how many turns in a coil, the principle of 
winding is the same. 

I have shown the ring winding first, because it is so simple 
that it can be understood with the most superficial explanation. 
The drum winding, which is used to a much greater extent, is the 
same in principle as the ring, but owing to the fact that the coils 
cross each other at the ends, it appears to be decidedly different. 
By the aid of Figs. 41 to 44, the drum winding can be made per- 
fectly clear. 

Fig» 4 J shows a ring armature core with a single coil wound 
upon it ; and Fig. 42 shows a drum core, with a single coil wound 
upon it. In the ring, only one side of the coil appears upon the 
outer surface of the armature, but in the drum, as there is no 
open space for the coil to thread through, both sides of the coil 
must be placed upon the outer surface. The side B of the coil 
may be called the live side, as it is the one from which the ends 
project, and the lower side c, may be called the dead side. Since 
only the live side of the coil has ends to be connected, it can be 
readily seen that if in the drum winding we leave spaces between 
the live sides for the dead sides, and then connect the ends of the 
live sides by jumjiing over the dead side between them, that we 
will have the same order of connection as in the ring winding. 



HANDBOOK ON ENGINEERING. 



29 




Fig. 41.' 




The dead side of each coil adjoins the live side of a coil that is, in 
reality, half a circumference away from it; thus, in Fig. 43, the 
live side of coil (/ is at the top and the dead side is at the bottom ; 
while the live side of coil n is at the bottom and the dead side is 
at the top. The live sides of these two coils are on opposite sides 
of the armature, so that the coil side to the right of a is simply 




Fiff. 43. 




30 HANDBOOK ON ENGINEERING. 

the dead side of a coil whose live side is on the other side of the 
diameter. In Fig. 44 the two coils a and h are adjoining coils, 
for the coil side between them is the dead side of coil n. To con- 
nect the armature, therefore, we join end 2 of coil a with end 1 
of coil ?>, and the end 2 of coil h would jumj) over a dead side and 
connect with end 1 of coil c. Coil c, however, would appear to 
be two coils ahead of ?>, just as h appears to be two coils ahead 
of a. 

In winding drum armatures, the coils are generally placed in 
pairs, as shown in Fig. 43 and also in Fig. 44. The object of 
this is simply to make the ends of the armature look more even* 
A drum armature can be wound out of a continuous wire, by 
simply making a loop to take the place of the ends 1 and 2, and 
then skipping a space, as shown by coils a and h in Fig. 44. After 
the armature is half covered, there will be spaces left between the 
coils, these spaces being of the width of a coil ; we then proceed 
to fill up the vacant spaces, and when they are all tilled, the last 
coil j)ut in will be the proper position to connect with the first 
one wound. A little practice with a piece of twine and a wooden 
cylinder, will enable any one to find out in short order how to 
wind drum armatures. 

The two types of winding I have explained, are those used 
with two pole machines, motors as well as generators. I may 
here add that there is no difference, electrically, between a motor 
and a generator, and any machine can be used for either service. 
Motors, however, are somewhat modified in design so as to make 
them more suited to the work they have to perform. The modi- 
fication consists mainly in protecting the parts liable to ])e injured 
by objects falling upon them. 

The g'eneral arrangement of the field and armature in a two 
13ole machine is shown in Fig. 31. The design can be changed in 
a vast number of ways, but it will always be two-pole, or bipolar, 
as it is called, if onl}^ two poles are presented to the armature. 



HANDBOOK ON ENC41NEERING . 



31 



Generators and motors are arranged so that the current that 
magnetizes the field may be the whole current that flows in the 
circuit, or only a part of it. When the whole current passes 
through the field magnetizing coils, the machine is said to be of 
the series type ; this name being given because the armature wire 
and the field coils are connected in series, so that the current first 
passes through one and then through the other. If the field 
coils are traversed by only a portion of the current, the machine 




Fig. 45. 



Fig. 46. 



is said to be of the shunt type, owing to the fact that the field is 
supplied with a current that is shunted from the main circuit. 
Generators and motors are also arranged so that there are two 
sets of field coils and one is traversed by the w^hole current, and 
the other b}' a portion thereof. The best way to understand 
these different types of connection is by means of simple diagrams . 
that show the wire coils of the field and the outline of the arma- 
ture. Such diagrams are presented in Figs. 45 to 50. Fig. 45 



32 



HANDBOOK ON ENGINEERING. 



represents the series connection, A being the armature, C the 
commutator, and M the field coil. The direction of the current 
is indicated by the arrow heads. Fig. 46 is the shunt connection, 
and the arrow heads show^ the direction of the currents in the case 
of a generator. As will be seen, at d the field current branches 
off from the main line and returns to it at a, after having passed 
through the field coil. Fig. 47 shows the type in which the field is 
magnetized by two sets of coils, one being in series with the main 
circuit and the other in shunt. As will be noticed, all the 
armature current passing out through wire cZ, goes through coil 
F^ except the portion that is shunted at c, into the shunt coil M. 
This tyi^e of winding is called compound, being a combination 
of the series and shunt. When the shunt coil is connected as in 




Fio-. 47. 




^ Fig. 47, it is called a short shunt, and when as in Fig. 48, it is a 
long shunt. In tlio first case, the coil 3f shunts tlie armature 
only, and in the second, it shunts the coil F also. 



HANDBOOK ON E N G I X IC E KIN G . 



33 



Figs* 49 and 50 show the shunt and compound types for 
motors, and as will be noticed, the only difference between them 
and the generator diagrams, is that the direction of the current 




Fig. 49. 



Fig. 50. 



in the shunt coils is not the same. This difference in direction is 
due to the fact that in the generator the armature generates the 
current that passes through coil 31; hence, at point d, the cur- 
rent flows up to the main line and down to the Held coil. In the 
motor, the current comes from an external source through main 
n, and thus passes from a to the armature, and also to the field 
coil, thus traversing the latter in the opposite direction. In the 
series coil F, the direction of the current is the same in both 
machines. 

Generators are made so as to keep the strength of the current 
constant, and allow the voltage to vary as the demands of the 
service may require ; or they may be wound so as to keep the 
voltage constant and allow the current strength to vary. Machines 

3 



34 HANDBOOK ON ENGINEERING. 

of the first class are called constant current, and are 
used principally for arc lighting. Machines of the second 
class are called constant potential and are the kind used 
for incandescent lighting, for electric railways and for the 
operation of motors of every description. For constant current 
generators the series winding is used in connection with some 
kind of regulating device that prevents the current strength from 
varying more than the small fraction of an ampere. The shunt 
and compound windings are used for constant potential genera- 
tors. If the armature wire had no resistance, the shunt winding 
would enable a generator to maintain a constant voltage at its 
terminals, no matter how much the strength of the current might 
vary ; but armature without resistance cannot be made ; there- 
fore, a shunt-wound machine will develop a slightly lower voltage 
with full current than with a weak one, but the difference will 
not be more than three to five per cent. By the aid of the com- 
pound winding, the generator can be made so as to develop the 
same voltage with light or full load, and if desired, the voltage 
can be made to increase as the current increases. If a com- 
pound generator is so proportioned that the voltage is the same 
for weak and strong currents, it is said to be evenly-compounded, 
and if the voltage increases as the current increases, it is said to 
be over-compounded. If the voltage is five per cent higher, with 
full load than with no load, the generator is said to be over-com- 
pounded five per cent, and if the increase is ten per cent, it is 
said to be over-compounded ten per cent. 

The way in which a compound generator increases the volt- 
age can be readily understood from an examination of Fig. 47. 
The current that passes through the shunt coil M, is practically 
one of the same strength at all times ; therefore, the magnet- 
izing effect of this coil does not change. Through coil F the 
whole current passes, hence, tl\e magnetizing effect of this coil 
increases as the current strength increases. Now the total field 



HANDBOOK ON ENGINEERING. 35 

magnetism is that due to the combined action of the two coils, so 
that as the action of F increases, the strength of the field in- 
creases. If F has only a few turns of wire, it will only help 
slightly to magnetize the field ; therefore, its increased effect, due 
to increase in current, will not be very noticeable ; but if F has 
many turns, it will develop a large proportion of the field magnet- 
ism, and, under this condition, the change in current strength 
will make a decided change in the strength of the field, and thus 
in the voltage, for the voltage is directly proportional to the 
strength of the field. 

In motors, the coil F can be connected so as to act with 
coil 3/, or against it. If both coils act together, the motor is 
compound-wound ; and if F acts against ilf, the motor is differ- 
entially-wound. A compound-wound motor will slow down more 
with a heavy load than a simple shunt machine, but it will carry 
the load with a smaller current, and, on this account, this wind- 
ing is commonly used for elevator motors. A differential motor 
will hold up the speed better with a heavy load than a simple 
shunt niachine, but it will take a correspondingly larger current 
to do the work. The differential winding is not used to any great 
extent, except in cases where it is desired to obtain as uniform a 
velocity as possible. 

In explaining' the principles of armature winding, it was shown 
that the commutator brushes must make contact with the com- 
mutator on the sides, that is, that in Fig. 51, they would be 
placed on the diameter n n. In actual machines, they are either 
ahead of this line, as in Fig. 52, or back of it, as in Fig. 53. 
The first position is that of the generator and the second that of 
the motor. The reason why the brushes have to be set ahead of 
line n n in a generator, and back of the line in a motor, is that 
the armature current develops a magnetization of its own, and this 
reacts upon the magnetism of the field so as to twist the lines of 
force out of their true path. If we look at Fig. 39, we can see 



36 



HANDBOOK ON ENGINEERING. 



that the direction of the current through the wires is such that 
the magnetizing effect produced upon the armature core is the 
same as it would be if the wire were wound in the way indicated 
by the vertical lines in Fig. 51. Now this current will develop a 
magnetization in the direction of line n n; that is, at right angles 
to the field magnetism. These two magnetic forces of the arma- 
ture and the field, engage in a tug of war, and the result is that 
the actual magnetization that acts upon the armature wire is the 
combined effect of the two. If the strength of the field magnetism 




Fiff. 51, 



Fig. 53. 



is proportional to line c a, anti the strength of the armature mag- 
netization is proportional to line c ?>, then the actual magnetiza- 
tion will be equal to line c d, and in the direction d d. In Fig. 
52, which represents a generator, if the current in the field coils 
passes over the front side in the direction of arrow ^, and the 
armature revolves in the direction of arrow d, then the armature 
current will be in the direction of arrow /and the armature mag- 
netization will be in the direction of arrow h. The field magneti- 
zation will be from ^to ^S', therefore, the resulting magnetization 
will be in the direction of line a a. Now the proper position for 



HANDBOOK ON ENtJINKEKTNG. 37 

the brushes is on u Uiie at right augles to tlie direction of the 
field, hence, they must rest upon line c c. If the machine is a 
motor, the only change effected will be that the direction of the 
armature current will be reversed, so that arrow / will point 
downward instead of uj^ward, and the magnetism of the armature 
will be directed to the right as shown by arrow c. Under these 
conditions, the actual direction of the field magnetism will be that 
of line b b, and upon line e e, at right angles to this the brushes 
must be set. 



^C 







38 HANDBOOK ON ENGINEERING. 



chaptp:k IV. 

MULTIPOLAR MACHINES. 

The only difference between a bipolar and multipolar machine 
is, that the latter has two poles, and the former has two or more 
pairs of poles. In consequence of this difference in the number 




E 



Fio-. 54. 



of poles, the armature winding has to be slightly modified, as will 
be iDresently explained. Fig. 54 illustrates a four-j^ole machine 



HANDBOOK ON ENGINEERING. 



39 



and, as will be noticed, the N and jS poles alternate around the 
circle. This arrangement is followed, no matter what the number 
of poles may be. 

The advantage of the multipolar construction is that it in. 
creases the capacity of the machine for a given size and weight- 
Figs. 55 to 57 illustrate the gain effected in weight. The first 
figure shows a two-pole machine, the second a four-pole and the 
third an eight-pole, the three being of the same capacity. The 
poles of the second machine are half as wide as those of the first, 
as there are twice as many. The other parts are reduced in like 
proportion. In Fig. 57, the poles are one-quarter as wide as in 




Fig. 55. 



Fig. 56. 



Fig. 57. 



Fig. 55, as there are four times as many. On account of the 
reduction in the width of the poles, the armatures can be increased 
in diameter as the number of poles is increased, without increas- 
ing the outside dimensions of the machine, so that in reality, 
Fig. 56 is somewhat more powerful than Fig. 55, and Fig. 57 is 
still more powerful. 

The fields of multipolar machines are wound the same as 
those of the bipolar; that is, as series, shunt or compound. 
Figs. 58 to 60 show the three types of winding for a four-pole 
machine and Fig. 61 is a diagram of compound winding for an 
eight-pole generator. The number of commutator brushes used is 
equal to the number of poles, although with one type of armature 



40 



HANDBOOK ON ENGINEERING. 



winding, two brushes are sulllcient, no matter how many poles 
the machines may have. In practice, however, even with this 
winding, the number of brushes is generally made equal to the 
number of poles. 

With a fouf-pole machine the brushes can be connected in a 
simj^le manner, as shown in Figs. 58 to 60, but with a greater 
number of poles, two rings are generally provided, to which the 
brushes are connected in the manner shown in Fig. 61. 




Fig. 58. 



Fio;. 59. 



Looking at Fig-* 54, It can be seen that if the current flows up 
from the paper, under the ^ poles, it will flow down through the 
paper, under the /S' poles ; hence, the armature coils in a four- 
pole machine must span only one-quarter of the circumference, 
and not one-half, as in the two-pole armature. For a six-pole 
armature, the coils must span one-sixth of the circumference, 
and for an eight-pole, one-eighth, and so on, for any higher 
number of poles. 

There are two types of winding for multipolar armatures, one 
being called the lap, or parallel winding, and the other the wave 



HANDBOOK ON ENGINEERING. 



41 




42 



HANDBOOK ON ENGINEERING. 



or series winding. Fig. 62 is a diagrammatic illustration of the 
lap winding, and Fig. 63 of the wave winding, both for four poles. 




Fig. 62. 



The small circles around the outside of the armature represent 
bars or wires, which are connected with the commutator segments 
by means of the solid lines, and with each other at the opposite 
side of the armature, by means of the broken lines. 

If we start from coil side, or bar 1 on the left, and follow the 
connections as guided by the numbers, we will finally reach 32, 
and thus come back to left side brush a, which is the starting 
point. As will be seen, bar 1 connects at the back of armature. 



HANDBOOK ON ENGINP^ERING. 



43 



with bar 2, and then over the front, the connection runs in the 
backward direction, to bar 3 ; thence, forward again, at the back 
end, to bar 4, and again backward over the front, to bar 5. The 
connections, therefore, lap over each other and it is on this 
account, that it is called a lap winding. 

Fig", 63 shows the wave winding, and it will be noticed that if 
we start from bar 1 at the top, we advance around the right to bar 
2, and then we go further ahead to bar 3, and in like manner 
advance to bar 4, the connections in every case advancing in the 




Fig. 63. 



same direction around the circle. It will be further noticed that 
the connections run zig-zag from side to side of the armature core 



44 HANDBOOK ON ENGINEERING. 



I 



as they advauce, thus forming a wave-hke path for the current, 
and it is on this account that this style of connection is called 
wave winding. 

With the lap winding, the brushes (( a are connected with each 
other, and so are the h b brushes. In the wave winding, two 
brushes set one-quarter of the circle from each other, will take 
the current off properly as indicated by a and h in Fig. 63, but 
four brushes can also be used. 

In Figf. 54^ the brushes are shown midway between the poles, 
while in Figs. 62 and 63, they are opposite the poles. This dif- 
ference in position is due to the fact that in the last two named 
figures, the connections between the armature coils and the com- 
mutator segments do not run in radial lines from either side, but 
one connection bends backward and the other forward. In 
actual machines, the connections are run as in these diagrams, and 
in some cases, one of the sides runs in a radial direction; there- 
fore, in some generators, the brushes are opposite the poles, and 
in others they are between them. 

Diagframs 62 and 63 show coils of a single turn, but by regard- 
ing the broken lines as representing the position of the end of the 
coil at front as well as the back of the armature, and the solid 
lines as simply the ends of the wire that connect with the com- 
mutator segments, they become accurate representations of coils 
of any number of turns. 

The coils of multipolar armatures are made on forms, and in 
the finished state are placed upon the armature core. Some coils 
are so formed as to bend down over the ends of the armature, and 
are then given the form at the ends, shown in Fig. 64, so they 
may fit into each other. In some machines, the coils do not bend 
down over the ends of the armature, but run out parallel with 
the shaft. Armatures so wound are sometimes said to have a 
barrel winding, and the coils, if laid out upon a flat surface, 
would present the appearance of Fig. 65 ; that is, if the}' con- 



HANDBOOK ON ENGINEERING. 

abed 



45 




Fiff. 64. 



Fig. 65. 



tained more than one turn. If of the single-turn type, they 
would look like Fig. 66, if for a lap winding; and like Fig. 67, 
if for a wave winding, the ends d d being joined and then con- 
nected with the commutator segments. 

In connecting the field coils of multipolar machines, it is 
necessary to be careful not to make mistakes, so that some of the 



abc 



abc 



ab c 



WW w 



d 

Fig. 66. 




Fig. 67. 



46 HANDBOOK ON ENGINEERING. 

coils will act to magnetize the field in the wrong direction. By 
studying Fig. 27 and the explanation of it, the direction of the 
magnetic lines of force with respect to the direction of the current 
through the magnetizing coils, can be clearly understood, and 
then there will be no difficulty in determining the proper way in 
which to connect the coil ends, for all we have to do is to make 
the connections such that if one pole is N the one next to it is S. 
With two-pole machines, it is also necessary to be careful not to 
connect the field coils improperly; that is, if there is more than 
one coil, and in most machines this is the case. 

The current that energizes a magnet is called the magnetizing 
force and is measured in ampere turns. The ampere turns are 
obtained by multiplying the number of turns of wire in coil, by 
the amperes of current flowing through it. 

All forms of matter resist the development of magnetic force. 
This resistance is called magnetic reluctance. The reluctance of 
air is much greater than that of iron or steel, but is constant ; 
that of iron and steel is not. If one thousand ampere turns 
develop a certain magnetic density in a circuit composed wholly 
of air, two thousand ampere turns will double this density. In 
iron and steel it will require much more than double the ampere 
turns to double the magnetic density. 

If in a magnetic circuit ten inches long, 100 ampere turns 
develop a certain density, it will require 200 ampere turns to 
develop the same density if the magnetic circuit is double the 
length. The table on page 209 gives the ampere turns required 
to develop different magnetic densities in magnetic circuits one 
inch long, composed of air, iron and steel. 

To find ampere turns required to develop any magnetic density 
in any magnet use following rule : - — 

Multiply the figures given in the table on page 209 ; for density 
required, by length of the magnetic circuit, and the product will 
be total number of ampere turns. 



HANDBOOK ON ENGINEERING. 47 



CHAPTER V. 

SWITCH-BOARDS, DISTRIBUTING CIRCUITS AND SWITCH- 
BOARD INSTRUriENTS. 

Generators of the constant potential type are made so as to 
develop a certain voltage at a given velocity, but in some cases it 
is not practicable to run them at the exact speed for which they 
are designed ; and in others, it is desired to vary the voltage 
slightly, hence, all machines are i3rovided with means for chang- 
ing the e.m.f. slightly. This regulating device is also necessary 
in cases where the load is for a time light, and for the balance of 
the time heavy; for, as we have shown, the voltage will var}^ to 
some extent with changes in the strength of the current. If 
the generator is at some distance from the points where the cur- 
rent is used, the drop of voltage in the lines will be greater with 
strong currents ; hence, when the load is heavy, it is necessary to 
increase the voltage developed by the generator. As it is not 
advisable to change the speed of the engine, the variation of volt- 
age is obtained by changing the strength of the current that 
flows through the shunt field coils, and this is accomplished by 
providing a resistance that can be cut in or out of the shunt coil 
circuit, as is illustrated in Fig. 68, in which B represents the 
resistance, or field regulator, as it is called. When the lever is 
moved to the extreme left position, all the regulator resistance is 
cut out of the circuit, and then .the voltage of the generator is 
the highest that can be obtained with the speed at which it is run- 
ning. When the lever is moved to the extreme right, all the 
resistance of the regulator is introduced into the shunt coil cir- 
cuit, and then the voltage is the lowest. By placing the lever in 



48 



HANDBOOK ON ENGINEERING. 



intermediate positions between the extremes right and left, differ- 
ent voltages may be obtained. 

To be able to operate a generator furnishing current to a sys- 
tem of distributing wires, it is necessary to have a number of 




Fiff. 68. 



instruments and other devices, included in the circuit, some of 
which are absolutely indispensable, and others of which are simply 
conveniences, and may be looked upon as luxuries. The various 
devices required are shown in Fig. 69. The generator is shown 
at 3f, and at e the field regulator is placed, audit is connected 
with one of the generator armature terminals and with one end 
of the shunt coil wires by means of wires d d. The wires c c 
run from the generatoi* terminals to the voltmeter V, arid thus 
enable us to see what the voltage is at all times. Wires a and b 
convey the current to the external circuit, with which they can be 
connected or disconnected by means of switches ss ss. At A an 
ammeter is placed which indicates the strength of current *"^ 



HANDBOOK ON ENGINEERING, 



49 



amperes. The ammeter can be placed in either a or 6, as the 
same strength current flows in both. At// safety fuses are pro- 
vided, so as to open the circuit in case the current becomes so 
strong as to be capable of overheating the generator Avire. If one 
of the line wires runs out into the open air, and is carried along on 
poles, we will have to provide a lightning arrester, as shown at /i, 
this being connected with the ground as at g. If both lines run 
into the open air, an arrester must be placed in both ; and if 
both are confined to the interior of a building, no arresters will 
be required. From the points m m branch circuits may be run 
off in as many directions as necessary, and by providing switches 
s s, these can be connected or disconnected from the main line 
when desired. 

This crude arrangement would enable us to operate the system 
successfully, but it would not be so convenient as a more methodi- 




cal groujjing of the several devices and instruments. It repre- 
sents the way things were done in the early days of electric light- 
ing, but at the present time, instead of having the several parts 
scattered about in a helter-skelter fashion, they are all assembled 

4 



50 



HANDBOOK ON ENGINEERING. 



upon a large panel, which is called a switch-board. Fig. 70 gives 
the general arrangement of wiring and location of devices for a 
simple board arranged for one generator feeding into five external 




Fiff. 70. 



circuits. The ammeter and voltmeter are placed at the top of the 
board, and directly under these are arranged five switches, s, 
which control the external circuits. One of these circuits is indi- 



s 

\ HANDBOOK ON ENGINEERING. 51 

cated by the lines n p^ fj\ being safety fuses. The wires i i con- 
vey the niain current from the generator to a circuit breaker D, 
which is simply a switch that is constructed so that it will open 
automatically when the current becomes too strong. From the 
circuit breaker, the current passes through wires a and h to the 
main switch F^ and by ware c, it runs from here to the ammeter 
A and from the latter by wire cZ to a rod 1 which is called a bus 
bar. The upper side of the main switch is connected directly 
with bus 2. The voltmeter is connected with two busses by the 
wires e e. The field regulator is located back of the board at i?, 
and is connected in the shunt coil circuit by means of wires li li. 
The switch of the regulator R is connected with a hand-wheel on 
the front of the switch-board, so that the attendant can watch 
the voltmeter as he turns the wheel and thus see just what effect 
the movement is producing on the voltage. 

In addition to the devices shown in Fig. 70, we can, if desired, 
provide a recording ammeter, a recording voltmeter and a watt- 
meter ; the first two would give us a record of the amperes and 
volts for a certain length of time, generally 24 hours, and the 
last one would register the amount of electrical energy. We 
could also provide ammeters for each one of the distributing cir- 
cuits, so as to know the strength of current in each one. 

If we desire to arrange the switch-board for two generators, 
and these are of the shunt type, we will require no changes in 
^ig. 70, except to provide another regulator and a main switch 
•iud circuit breaker for the additional machine. This arrange- 
nent of board is suitable for a single compound wound generator, 
or any number of shunt wound machines, but if we have two or 
more compound generators, the connections between these and 
the bus bars will have to be somewhat modified. 

The modifications required in a switch-board for two or more 
compound generators can be made clear by the aid of Figs. 71 
and 72. In the first figure, we can see that if the current return- 



b2 



HANDBOOK ON ENGINEERING. 



jDg from the main line through n divides into wires a and /j, it 
will remain divided until it passes through the armatures and the 
F coils of the two machines, and thence through wires e e, it will 




reunite again in wire p. In Fig. 72, the two parts of the current 
will flow through wires d d to the single ware e, and then divide 
into wires /'/', and thus reach the coils F F, and, finally, through 
wires Ji h, reach j). In Fig. 71, if the right side armature gen- 
erates more current than the other one, the F coil of that gener- 
ator will be traversed by the strongest current, for in each machine 
the strength of current in the armature and the F coil will be 
nearly the same. Now, if the right side machine generates the 
strongest current, it is because its voltage is the highest, but the 
fact that its F coil will be traversed by the strongest current will 
make its voltage still higher, thus increasing the difficulty. In 
Fig. 72, the current flowing through the two F coils will be the 
same, no matter how much the two armature currents may differ, 



HANDBOOK ON ENCJINKEKING. 



53 



for these come together in wire (% and passing from this to the two 
i^ coils, the current will divide in equal amounts. As can be 
seen, the effect of adding the wires d d, e and// in Fig. 72 is to 
equalize the currents that flow through the F coils, and thus pre- 
vent, as far as possible, the unequal action of the generators. 

When two or more compound generators are connected so 
as to feed into the same general circuit, the connections are 
made in accordance with Fig. 72. Fig. 73 illustrates a switch- 
board for two compound generators, and, as will be noticed, the 
most striking difference between it and Fig. 70, is that there 
are three bus bars instead of two. One of these busses is 
called the equalizer, and it takes the place of wires d d p and 




//in Fig. 72. The equalizing connections run from generator 
wires /to the main switches yiS, and thence to bus 1. The h wires 
of the generators run to one side of the circuit breakers D E, 



54 



HANDBOOK ON ENGINEEKING. 



aud thence to the middle bhides of the aS switches, and from these 
to the bus 2. The generator wires run to the outside blades of 




Fiff. 73. 



the circuit breal^ers, and from these to the ammeters A A, and 
thence to bus 3. The voltmeters are connected with wires h and 
/, and thus indicate the e.m.f.'s of the generators. 



HANDBOOK ON ENGINEP]RING. 55 

If another geuerator were added, it would be connected with 
the bus bars in the same way. 

In starting two or more compound- wound generators, one 
machine is started first, and then the second is run up to full 
speed, and its voltage is adjusted by means of the regulator i2, so 
as to be the sam^ as that of the machine that is running. When 
the voltages of the two machines are equal, the main switch of 
the second machine is closed so as to connect it with the bus bars. 
This action will generally make a slight change in the voltage of 
the second machine, causing it to run up or down a trifle ; and as 
a result by looking at the ammeters, we will find that it is taking 
more or less than its share of the load. If such is the case, we 
manipulate the regulator i?, until the loads are properly divided. 
Whether the voltage of the second machine will rise or fall after 
(t is connected with the bus bars, will depend upon the extent to 
which it is compounded ; if slightly compounded, the voltage will 
drop, and if heavily compounded, it will rise. 

The switch-boards illustrated are adapted to what is called the 
two-wire system of distribution, but in cases where it is desired 
to transmit the current to a considerable distance, without using 
extra large wire, the three-wire system of distribution is 
employed. This system is illustrated in Figs. 74 to 76. 

Suppose we have two generators as indicated at G G in these 
diagrams, and let the direction of the current through both be 
from bottom toward the top ; then it is evident, that if we remove 
the middle wire 0, the lower machine will deliver current into the 
upper one, and if each generator develops an e.m.f. of 115 volts, 
the combined e.m.f. will be 230 volts, and this will be the 
pressure between the bottom and top wires ; but the voltage 
between either wire and the center one will only be 115. Suppose 
we have a number of lamps connected between wire P and the 
center wire 0, and an equal number of lamps between and ^5 
as is shown in Fig. 74 ; then it is evident that the same amount 



56 



HANDBOOK ON ENGINEERING. 



of current will flow through both sets, and as a eoiiseiiuenee, all 
the current that passes from the upper generator into wire P will 
go directly through both sets of lamps to the lower wire N^ and 
thus return to the lower side of the bottom generator. Under 



9a,haha9aha 44 



\f \' •«' \f 



?- % ?- ?° ?' ??" 



s 



rara 



re 4 4 



WdS>d 



Qn. a Q 



>' \f V 



6)^ ©B @C 



t»?''P-'P- . 



these conditions, the lamps will be acted upon by 115 volts each, 
but the current will be driven through the circuit by a voltage of 
230. Now, if the voltage is doubled, four times the number of 
lamps can be supplied with the same size wires ; hence, the cost 
of line wire per lamjD will be reduced to one-fourth. Suppose, 
that instead of having the lamps equally divided as in Fig. 74, 



HANDBOOK ON ENGINEERING. 57 

they are arranged as in Fig. 75 ; then since the current fed into 
the system from the upper wireP is only sufficient for five lamps, 
while there are seven lamps in the lower section, it follows that 
through wire a current sufficient for two lamps must be sup- 
plied. The way in which the currents would flow in this case is 
clearly indicated by the arrows. 

In Fig* 74, it will be seen that if we removed the middle wire, 
the lamps would not be affected, for none of the current comes 
through it; but in Fig. 75, if we cut the middle wire, two of the 
lower lamps would be unprovided for. From this it will be seen 
that the object of the middle wire is simply to provide the extra 
current required for the side that carries the largest number of 
lamps. If the lights are so arranged that on both sides of the 
central wire the number is practically the same at all times, 
the center wire can be made very small, but such perfect balance 
cannot be obtained always, and on that account, the center, or 
neutral wire, as it is called, is made of the same size as the 
others, except in large systems, in which it is sometimes not more 
than one-third the size. 

As motors require large amounts of current, they are nearly 
always made to operate with a voltage of 230, and are connected 
with the outside wires of the system, as is shown in Fig. 76, in 
which a a a a and c c c c indicate lamps connected between the 
sides and the neutral wire, and ABC are motors connected 
across the outside lines. 

When a switch-board is arranged for two generators connected 
with a three-wire system, we use three bus bars, just as in Fig. 
70, but discard the equalizing connection, and connect the 
generators with the busses in the same way as they are connected 
with wires N and P in Figs. 74 to 76. If we have a number of 
generators feeding into the three-wire system, then we connect 
each set with an equalizer bus ; that is, provide two sets of 
busses, and the P and N busses of these two sets we connect 



58 



HANDBOOK ON ENGINEERING. 



with a third set in the proper order for the three-wire system, 
and from tlie latter busses the external circuits are fed. 

If we desire to supply a larger building with a lighting and 
power system, we can run the wires in almost any way, providing 
we make connections with the lamps and motors, but if we adopt 



^^rr^ 



=a^ 



TC 



=oa 



=aa 



=aa 




D 

=0= 



0= 



D 



-o- 

0^ 



o- 



Fig. 77. 



a systematic arrangement it will require less labor to operate the 
plant, and when anything goes wrong we will be able to locate 
the difficulty with much less trouble and in less time. The best 
way to accomplish this is by the use of small switch-boards 
located at different points in the building, these becoming centers 



HANDBOOK ON ENGINEERING. 59 

of distribution, from wliich all the lamps are supplied. The 
general arrangement of such a system can be understood from 
Fig. 77, in which B represents the main switch-board, located in 
the engme room, and e e e the several floors upon which the lights 
are located. From the main switch-board we run up four lines, 
one to each floor, and locate secondary boards at (7 and D D D. 
We can also run out lines directly from the board to the lamp 
circuits as at c c c c. From the boards C O, we run circuits to 
smaller boards, as shown at E, F, A, A, A, and h h h. From 
each one of these small boards we can ruu out circuits to the 
lamps. 

These small switch-boards are called panel boards or boxes, 
and also distribution boards. They are made of all sizes from 
eight or ten inches square, up to four or five feet, and are 
arranged to feed into one or two, or fifty or sixty circuits, 
supplying anywhere from five or six lights up to a thousand or 
more. 

The construction of distribution boards can be understood 
from Figs. 78 and 79, the first being arranged for the three- 
wire system, and the second for the two-wire. Fig. 78 is ar- 
ranged to feed ten circuits, and is provided with one main switch 
by means of which the entire box can be disconnected from the 
main line. The distributing circuits are provided with safety 
safety fuses on the outside wires, so that if anything goes wrong 
and the current increases to a dangerous point, the circuit will be 
open. No fuse is placed on the middle wire, as it is not neces- 
sary, and might result in cutting out both sides of the circuit 
when only one was disabled. 

Fig. 79 is a more complete j)anel, because each one of the six 
distribution circuits is provided with a switch, so that it is pos- 
sible to disconnect any of the circuits without interfering with the 
others. In some cases a distribution board of this kind is the 
only thing that will answer the purpose, but in others, the more 



60 



HANDBOOK ON ENGINEERING. 



simple construction of Fig. 7<S iinswcrs Just us well. The fuses 
in Fig 78 are shown at E F. These fuses are sometimes made so 
that they can ])e used as switches ; that is, they can be pulled out 





Fig. 78. 



Fig. 79. 



of place and thus open the circuit, and if one blows out it can be 
removed and a new fuse be put in, and then it can be replaced, 
thus placing the disabled circuit in service without interfering 
with the others. 

The ammeters and voltmeters used on switch-boards depend 
for their operation upon the repulsion between magnetic lines of 
force. A great many different constructions are used, but most 
of them operate upon the principles illustrated in Fig. 80 or 81. 
If a small bar of iron c is placed between the poles of a permanent 
magnet, as in Fig. 80, it will be held in the horizontal position by 
the attraction of the magnet. If it is surrounded by a stationary 
coil of wire 6, through which a current of electricity passes, then 



HANDBOOK ON ENGINEERING. 



61 



it will be under the influence of two forces, one the attraction of 
the poles N jS of the magnet, and the other the attraction of the 
lines of force developed by the current flowing through coil b. 
The action of the latter will tend to swing the rod c into the ver- 
tical position. The force of the magnet will remain constant, but 
the force of the coil will vary with the strength of the current 
l^assing through it; hence, the stronger the current the more the 
bar c will be swung around into the vertical position. If we pro- 
vide a small counter-weight, as shown in the illustration, to resist 
the action of the coil, we will have a means that will enable us to 
adjust the movement of the bar, so that it will swing around 
through a given angle for a given increase in current. If a 
l^ointer a is secured to c it will swing over the scale as shown, 
when c is rotated by the action of the coil. 

If coil b is mounted so that it may swing around the center 
pivot, we can discard bar c, for then as soon as a current traverses 
b, the lines of force developed around it will be attracted by 




Fig. 80. 



Fig. 81. 



those of the permanent magnet, and will exert a twisting force so 
as to place the axis of the coil parallel with the lines of force 
passing from K to S. In this case as in the previous case, the 



62 



HANDBOOK ON ENGINP^ERING. 



effort to twist b arouud will be proportional to the strength of 
the current, hence, the stronger the current the greater the 
swing. Ammeters and voltmeters are made on these principles, 
and the only difference in the two instruments is in the size of 
the wire used for the coils. 

Fi^s, 82 and 83 illustrate the principle upon which circuit 
breakers are made. In Fig. 82, suppose a current flows through 
magnet E, then it will attract the lever A, the latter being made 




Pf^ 




c^'^'^-- 



Fiff. 82. 



•^o 



Fi^. 83. 



of iron. If the current is weak it may not develop a sufficient 
attractive force in E to lift the weight D, and in that case A will 
remain where it is. If, however, the current is increased until E 
becomes strong enough to lift D, then A will move over toward 
the magnet, and the catch " a " falling behind it, will not allow 
it to return to its former position until placed there by hand. 
When A swings over, it carries 5, and thus breaks the connec- 
tion with C and opens the circuit. Thus it will be seen that by 
properly adjusting the weight TJ and the magnet E, we can set the 
device so as to open the circuit whenever the current reaches a 
certain strength. This is tlie principle upon which circuit break- 



HANDBOOK ON ENGINEERING. 63 

ers act, but such a device as Fig. 82 would be of no service for 
lighting circuits, because the distance by which C and B are 
separated is too small to break the current. By modifying the 
construction as in Fig. 83, we can obtain a device that will give a 
wide separation at the breaking point. In this construction, the 
lever A when drawn towards the magnet, strikes the catch a, so 
as to release lever S, and then the weight D throws the latter 
down to the position shown in broken lines, thus giving a wide 
separation between F and C. By moving the weight on the lower 
arm at A^ the device can be adjusted so as to act with different 
strengths of current. 

Circuit breakers as actually constructed, do not have the 
appearance of this diagram, but they operate on the principle 
illustrated by it. 

The electromotive in volts force developed in the armature of 
a motor, or generator, can be determined if we know the number 
of wires upon the outer surface, the number of maxwells of mag- 
netic flux that pass through the armature and the revolutions per 
second. The rule for the calculation is as follows : — 

Multiply the number of wires on the outer surface of the arma- 
ture by the maxwells of magnetic flux and by the revolutions per 
second, and divide this product by 100,000,000. 

This is the rule for two pole armatures. For multipolar arma- 
tures with series, or wave winding, use same rule making the 
flux equal to the sum of the fluxes issuing from all the positive poles. 

For multipolar armatures with a lap, or parallel winding, use 
same rule but take the flux issuing from one pole only. 

To obtain the pull in pounds of a motor armature at one foot 
radius use the following rule : — 

Multiply the number of wires on the outer surface of armature 
ibj the amperes of armature current, and by total number of max- 
wells of magnetic flux passing through armature, and divide this 
product by 852,000,000. See pages 13 and 46. 



64 HANDBOOK ON ENGINEERING. 

CHAPTER VI. 
ELECTRIC MOTORS. 

Motors are made so as to run at a constant velocity, or for 
variable speed. For the latter type of machine, the field coils are 
wound in series, and for constant speed the shunt winding is used. 
A motor of either kind cannot be started successfully without 
placing an external resistance in the armature circuit, because, 
when the armature is at a standstill, there is nothing but the 
resistance of the wire to hold the current back, and as a result, if 
no extra resistance is j^rovided, the first rush of current would be 
very great. As soon as the armature begins to revolve, an e.m.f. 
is induced in its wires, and this acts in opposition to the e.m.f. 
of the line current ; that is, it acts like a back pressure, and holds 
the current back. On this account, the e.m.f. of a motor is 
called a counter e.m.f., and it is abbreviated into c. e.m.f. 

The way in which the external resistance is connected with 
a motor is illustrated in Fig. 84, in which M is the motor and 
R the external resistance. Z) is a main switch, by means of 
which the motor is connected with the main line. This switch is 
closed first, and then switch F is moved to the right until it cov- 
ers the first contact of the resistance R. The current can then 
pass directly to the field shunt coils through wire e, and thence by 
wire a, return to the mainline. The armature current, however, 
has to first pass through the resistance i?, before it can reach wire 
i, and thus the armature. As soon as the armature begins to 
speed up, the switch F is advanced, step by step, and in a f,ew 
seconds it is moved to the extreme right position, in which all the 
resistance R is cut out of the armature circuit. When F reaches 
this position, the motor should be running at full speed. 



HANDBOOK ON ENGINEERING. 



65 



If the current should stop while the motor is running, the 
machine would stop, also, and then, if the current were turned 
on again, the motor would be caught with the armature connected 
across the line without an external resistance, and as it would be 
at a standstill, the current would rise to an enormous strength. 
To prevent this, the switch F is always opened whenever the motor 
stops. The attendant may forget to do this, however; therefore 
automatic switches have been devised that will open themselves 
whenever the current dies out. 




Fip\ 84. 



A simple switch provided with a resistance so as to be suited 
to start a motor, is called a motor-starter, and one that in addi- 
tion is provided with means for automatically flying to the open 
position whenever the current fails, is called an automatic under- 
load starter. 

If the motor is very much overloaded, its speed will slow down 
and the current will increase in strength. If the overload is suf- 
ficient, the current will become so strong as to be able to ourn out 



66 



HANDBOOK ON ENGINEERING. 



the armature ; hence, it is desirable to provide a circuit breaker 
that will open the circuit when the current becomes so strong as 
to be liable to burn out the machine. Motor-starters are made 
with a circuit-breaking attachment, and are then called automatic 
overload motor-starters. A device that combines the under and 
overload starter, features is called an automatic under and over- 
load starter, and by some people it is called a " no voltage " and 
" overload starter." 

When motors were first introduced, a great deal of trouble 
was experienced with the starters, owing to the fact that they 
were arranged so that when the motor was stopped, the connection 
with the field coils was broken. Now, the current flowing through 
the field coils objects to stop flowing when the connection is 
broken, and, consequently, it continues to flow between the end of 
switch i^in Fig. 84, and the last of the contacts of 72, until the 
distance is more than the e.m.f. of the current can overcome. 




Fig. 85. 



This action produces serious sparking at the last terminal, and im 
addition, produces a severe strain u])on the insulation of the 



HANDBOOK ON ENGINEERING. 



67 



field coils, because, as the current is headed off in one direction, 
it tries to find an outlet in another. This action is what is 




Fig. 86. 



commonly called the ' ' kick of the motor field . ' ' All this 
trouble can be obviated by connecting the starter with the motor 
in such a way that the field circuit is never opened, as is shown 
in Fig. 84. As this is quite an important point, I will present 
it in a more simple form in Fig. 85, in which it will be seen that 
the field coils and armature are permanently connected, so that 
when switch S opens the circuit, the field current can fiow through 
the armature, until it dies out. All first-class concerns make 
motor starters with this connection, at the present time. Some 
of them add the curved contact e. Without this contact, it can 
be seen that when the switch ^S' is moved to the top position, the 



68 HANDBOOK ON ENGINEERING. 

resistance 7^ is simply transferred from the armature to the field 
circuit, and that the current going to the field coils has to pass 
through this resistance. As this resistance is insignificant in 
comparison with that of the shunt coils, it makes little difference 
whether it is left in the field circuit or not, but by the addition of 
e it can be cut out. 

Variable speed motors are always arranged so that the speed 
may be changed by hand as conditions may require. Trolley-car 
motors are of this type, and so are the motors used for j^rinting 
presses, and many other kinds of work. Figs. 86 to 88 show 
arrangements by means of which the speed may be yaried with 
series wound motors. In Fig. 86, £' is the starting box and F is 
the speed regulator. In the act of starting, the switches are in 
the position shown. To start, the switch S and E is turned so 
as to close the circuit with the resistance R all included. S is 
moved toward the left as the armature speeds up, and reaches 
the last position when full speed is attained. If the switch of F 
is now closed, a portion of the current will be diverted from the 
armature, and thus its rotating force will be reduced, and thereby 
its speed. This method of speed control is also arranged so 
that the two switches act together, so as to introduce resistance 
into the motor circuit, and at the same time divert more or less 
of the current around the armature. It is not used extensively, 
as all the current that passes through F is just so much thrown 
away. 

In Fig* 87 the speed is controlled by means of the switch F^ 
which cuts out portions of the field coils and this changes the 
strength of the field. With this arrangement, if a portion of 
the field is cut out, the motor will run faster, because the c.e.m.f 
will be reduced, therefore, the armature current will be increased. 
To obtain a wide range of regulation, it is necessary to wind a 
large number of turns of wire on the field, so that with all the 
wire in service, the speed may be the lowest required. 



HANDBOOK ON ENGINEERING. 



69 



Fig"* SS shows iiuothcr arningeiiiciit that varies the streugth of 
the held by diverting a portion of the cnrreut tin"ough switch F. 
It gives as wide a range of regulation as Fig. 87, but is not so 
economical. 

Fig's. 36 and 88 cannot be used to regulate the sjjeed of shunt 
motors, but Fig. 87 can. The first two named figures, if used 




Plo-. 87. 



with a shunt motor, would simply afford a third path through 
which current could pass from one side of line to the other, that 
is, from the j) to the n wires, but this w^ould not materially affect 
the strength of current that would flow through the armature and 
field coils. They work with series wound motors, because the 
current is not shunted from wire jp to wire n but simply from 
one side of the armature, or the field, to the other. 



70 



HANDBOOK ON ENGINEERING. 



Fig". 89 allows au arniugeiiieut by means of which a shunt 
motor can be made for variable speed. In this case, the switch 





^m^ 



Fio-. 88. 



and resistance E is simply an ordinary starter, and i^ is a resist- 
ance that is introduced in the field circuit, so as to vary the 
strength of the field. With this arrangement the slowest speed is 
obtained when all the resistance of F is out of the circuit. 

The direction in which a motor runs can be reversed by sim- 
ply reversing the direction of the current through the armature. 
Any of the arrangements for varying the speed can be used in 
connection with reversible motors by arranging the switch so as 



HANDBOOK ON ENC4INEERING. 



71 



to reverse the armature connections. Fig. 90 will give a fair 
idea of the way in which a reversing switch is made. This repre- 
sents the type of switch used most generally for this purpose, and 
it is known as the cylinder switch. It is the kind used on trol- 
ley-cars. The vertical row of circles numbered from one to 
eleven represents stationary contact pieces, to whicli the terminals 
of the motor, the line and the resistance are attached. The 
shaded parts B B are metal plates that are secured to the 
surface of a cylinder, that is so located that as it is turned in one 
direction or the other, these plates slide over the stationary con- 
tacts. If the cylinder is turned so that the plates on the right 
side slide over the contacts, the motor will run in one direction, 
and if the cylinder is turned in the other direction, the motor will 
be reversed. Suppose the right side plates slide over the con- 




Fi^. 89. 



tacts, then the current f rom j^ will jjass to contact 2, and thence 
to wire a, and to the left-side of the field. Through wire d it 
will return from the field to contact 5, and by means of 



■72 



HANDBOOK ON ENGINEERING. 



plates JV^ mid 7', whicli tire connected as shown at X\ it will reucli 
contact o and wire h, which runs to the lower side of the arma- 
ture. From the top of the armature, through wire r, the current 
will return to contact 4 and tlirougii plates ^S' and M and the con- 
nection X will reach contact 6, which l^y one of the wires p con- 




Fio-. 90. 



nects with the left-side of the resistance D. From the right-side 
of this resistance, the current will jjass to contact 10, and thus 
to contact 11, through the cylinder plate, and in that way reach 
line wire 7i. 

If the cylinder i« turned further around, contact 7 will be coy- 
ered by plate 3f , and this will cut one section of 7). By a further 



HANDBOOK ON ENGINEERING. 73 

movement., contact 8 will be covered, thus cutting out another 
section, and by continuing the movement, all of D can be cut out. 

If the cylinder i^^ turned so as to slide the left-side plates over 
the contacts, the change effected will be that contact 5 will be 
connected with 4 instead of with 3, and contact 6 will be con- 
nected with 3 instead of 4, thus reversing the direction of the 
current through the armature. 

The strength of an electric current is measured in amperes. 
The electromotive force that drives an electric current through a 
circuit is measured in volts. The resistance that a wire or other 
circuit offers to the passage of an electric current through it is 
measured in ohms. 

The unit of resistance, the Ohm, is the resistance of a column 
of mercury about 40 inches long and about five hundredths of an 
inch in diameter, or, to be more exact, 106 centimeters long, and 
one millimeter in diameter. 

THE WATT. 

The watt is the unit of electric power— the volt ampere, the 
power developed, and is equal to ^Jg- of one horse power. A con- 
venient multiple of this is called the Kilowatt, written K. W,, and 
is equal to 1,000 watts. 

THE AflPERE. 

The ampere is the practical unit of electric current, such a cur- 
rent [or rate of flow, or transmission of electricity] as would 
pass, with an electromotive force of one volt, through a circuit 
whose resistance is equal to one ohm ; a current of such a strength 
as would deposit from solution .006 084 grains of copper per 

second. 

CANDLE POWER. 

The candle power is the unit of light ; and a standard candle 
is a candle of definite composition which with a given consump- 
tion in a given time, will produce a light of a fixed and definite 
brightness. A candle which burns 120 grains of spermaceti wax 
per hour, or two grains per minute, will give an illumination 
equal to one standard candle. 



7'4 HANDBOOK ON ENGINEERING. 



CHAPTER VII. 

INSTRUCTIONS FOR INSTALLING AND OPERATING SLOW AND 
MODERATE SPEED GENERATORS AND MOTORS. 

To remove the armature, take off the brush-holders, brush 
yoke, pulley and bearing caps and put a sling on the armature, as 
shown in accompanying illustration. The rope should make two 
or more turns about the commutator and each turn should lie 
straight and flat. A spreader of suitable length should be used 
and its location adjusted to prevent the rope from drawing against 
the flange or end connections, by tying a double knot in the sling? 
as shown. After the armature has been raised free from the 
bearings, the sleeves can be taken off and the armature sup 
ported in some convenient place by arranging blocks under the 
shaft at either end. 

In assembling, marked parts of the machine should be assem- 
bled strictly according to the marking. Clean all connection 
joints carefully before clamping them together. Wipe the shaft- 
bearing sleeves and oil cellars perfectly clean and free from grit. 
Place the bearing sleeves and oil rings in position on the shaft 
and then lower the armature into place, taking care that the oil 
rings are not jammed or sprung. As soon as the armature is in 
position, pour a little oil in the bearing sleeves, put the cap on 
the boxes and screw them down snugly. If the caps are not put 
on immediately, the boxes should be covered to prevent dirt or 
grit falling into the bearings. The top fleld should next be put 
on and bolted firmly into position, and a level placed on the shaft 
to check the leveling of the foundation. 

Fill the bearings with the best grade of thin lubricating oil and 



HANDBOOK ON ENGINP:ERING. 



75 



do not allow it to overflow. Oil throwing is usually due to an ex- 
cess of oil and can be avoided by care in filling the oil cellars. 




To complete the assembly, place the pulley on the shaft, draw 
up the set screws and put on the brush rigging and connection 
blocks. 

BRUSH SETTING. 

Place the brush-holders on the studs so that the boxes (^) 
which hold the brushes, shall be about i" from the surface of the 
commutator, and clamp them firmly in this position. From time 
to time the brush-holders should be turned slightly on the studs, 
to compensate for the wear of the commutator. 

Place the brushes in the holders, as shown in the figure and 
screw down the j^ressure spring " JB " by turning the nut (7, so 
as to give about 1^ lbs. pressure for li" brushes and J lb. for 
f" brushes. Nothing is gained by increasing the pressure per 



7H 



HANDBOOK ON ENGINEERING. 



squuru iucli on a carbon brush above two pounds, as the resist- 
ance per square inch beyond this point is practically not reduced. 




whereas, the friction is increased in direct proportion to the 
pressure. 




Fit the carbon brushes carefully to the commutator by j)assing 
beneath them No. sandpaper, the rough side against the brush 



HANDBOOK ON ENGINEP^RING. 77 

and the smooth side held down closely against the surface of the 
commutator. Move the sandpaper in the direction of rotation of 
the armature, and on drawing it back for the next cut, raise the 
brush so as to free it from the sandpaper, then lower the brush 
and repeat the operation nntil a perfect fit is obtained. If the 
brush requires considerable sandpapering, No. 2 sandpaper may 
be used at first, but the final fitting must be done with No. 0. 
If an attempt be made to fit the brushes without raising them 
when drawing the sandpaper back, it will in every case fail to 
give satisfactory results. When thick brushes are used — say 
J" — in addition to following the above instructions, the machine 
should be run as long as convenient without load in order to 
improve their surface. As soon as the brushes of a set appear 
to make a good fit, one of them should be removed from the 
brush-holders in the following manner, to determine if they are 
worn to a surface. 

Unscrew the stud Z), thereby freeing the end of the pig-tail 
E, and push the spring B forward, so that there will be j^lenty 



of room to draw the tip E on the end of the pig-tail through 
the slot F. Then draw the pig-tail through the slot F, bend it 



78 HANDBOOK ON ENGINEERING. 

forward and turn the spring B to one side, as shown in the 
last cut. The brush may then be withdrawn from the box. 
In replacing the brush, these directions should be followed in 
reverse order. 

Care should be taken not to disturb the nut C, after it has once 
been set, as it is not necessary to alter the pressure of the spring 
B in removing or replacing a brush. By this means a practically 
constant pressure may be kept on the brush. 

STARTING. 

Before putting on the belt, see that all screws and nuts are 
tight and turn the armature by hand to see that it is free and 
does not rub or bind at any point. Put on the belt with the 
machine so placed on the rails as to have the minimum dis- 
tance between pulley centers. Start the machine up slowly and 
see that the oil rings in bearings are in motion. As the machine 
comes up to speed, tighten the belt till it runs smoothly, and run 
the machine long enough without load to make sure that the bear- 
ings are in perfect condition. The bearings, when running, 
should be examined at least once a week. When it is neces- 
sary to renew the oil, draw the old oil from the reservoir 
through the opening in the side of the pedestal. 

CARE OF COMMUTATOR. 

The commutator brushes and brush-holders should at all 
times be kept perfectly clean and free from carbon or other dust. 
Wipe the commutator from time to time with a piece of canvas 
lightly coated with vaseline. If vaseline is not at hand, use oil, 
but lubricant of any kind should be applied very sparingly. 

If a commutator when set up begins to give trouble by rough- 
ness, with attendant sparking and excessive heating, it is neces- 
sary to immediately take measures to smooth the surface. Any 



HANDBOOK ON ENGINEERING. 79. 

delay will aggravate the trouble, and eventually cause high tem- 
peratures, throwing off solder, and possibly displacement of the 
segments. No. sandpaper, fitted to a segment of wood, with a 
radius equal to that of the commutator, if applied in time to the 
surface when running at full speed (and if possible with brushes 
raised) , and kept moving laterally back and forth on the commu- 
tator, will usually remedy the fault. If this does not suffice, it 
will then be necessary to tighten up the se'gments and turn them 
off true. A machine tool will not leave the surface smooth 
enough to. give perfectly satisfactory results. It is always neces- 
sary before putting on the load, after the commutator has been 
turned, to carefully smooth the surface with the finest sandpaper, 
thus removing all traces of the tool point. 

GENERATORS. 

As soon as the machine is set up and in running order, see 
that it excites itself and comes up to full voltage. If it does 
not, trace out the field connections and test the polarity. The 
trouble will probably be found in improper field connections. 

When the machine is to be run in parallel with other 
machines, and the direction of the current is found to be opposite 
to that desired, raise the brushes and excite the fields by closing 
the main switch from the bus-bars. 

DIRECTIONS FOR STARTING DYNAMOS. 

General. — Make sure that the machine is clean through- 
out, especially the comrnutator, brushes, electrical connections, 
etc. Remove any metal dust, as it is very likely to make a 
ground or short circuit. 

Examine the entire machine carefully, and see that there are 
no screws or other parts that are loose or out of place. See that 
the oil-cups have a sufficient supj^ly of oil, and that the passages 



.80 HANDBOOK ON ENGINP^ERTNG. 

for the oil are clean and the feed is at the proper rate. In the 
case of self-oihng bearings, see that the rings or other means for 
carrying the oil work freely. See that the belt is in place and 
has the proper tension. If it is the first time the machine is 
started, it should be turned a few times by hand, or very slowly, 
in order to see if the shaft revolves easily and the belt runs in 
centers of pulleys. 

The brushes should now be carefully examined and adjusted 
to make good contact with the commutator and at the proper 
point, the switches connecting the machine to the circuit being 
left open. The machine should then be started with care 
and brought up to full speed, gradually if possible ; and in any 
case the person who starts either a dynamo or a motor should 
closely watch the machine and everything connected with it, and 
be ready to throw it out of circuit if it is connected, and shut 
down and stop it instantly if the least thing seems to be wrong, 
and should then be sure to find out and correct the trouble 
before starting again. 

STARTING A DYNAHO. 

In the case of a dynamo it is usually brought up to speed 
either by starting up a steam-engine or by connecting the 
dynamo to a source of power alread}^ in motion. The former 
should, of course, only be attempted by a person competent to 
manage steam-engines and familiar with the particular type in 
question. This requires special knowledge acquired by experi- 
ence, as there are many j^oints to appreciate and attend to, the 
neglect of any of which might cause serious trouble. For ex- 
ample, the presence of water in the cylinder might knock out the 
cylinder-head ; the failure to set the feed of the oil-cups properly 
might cause the j^iston-rod, shaft, or other part, to cut. And 
other great or small damage might lie done by ignorance or care- 



HANDBOOK ON ENGINIOKKING . 81 

lessness. The mere mechanical conuecting of a dynamo to a 
source of power is usually not very difficult ; nevertheless, it 
should be done carefully and intelligently, even if it only requires 
throwing in a friction-clutch or shifting a belt from a loose pul- 
ley. To put a belt on a pulley in motion is difficult and danger- 
ous, particularly if the belt is large or the speed is high, and 
should not be tried except by a person who knows just how to do 
it. Even if a stick is used for this purpose, it is apt to be caught 
and thrown around by the machinery, unless it is used in exactly 
the right way. 

It has been customary to bring dynamos to full speed before 
the brushes are lowered into contact with the commutator ; but 
this is not necessary, provided the dynamo is not allowed to turn 
backwards, which sometimes occurs from carelessness in starting, 
and might injure copper brushes by causing them to catch in the 
commutator. If the brushes are put in contact before starting, 
they can be more easily and perfectly adjusted, and the e.m.f . 
will come up slowly, so that any fault or difficulty will develop 
gradually and can be corrected ; or the machine can be stopped, 
before any injury is done to it or to the system. In fact, if the 
machine is working along on a system, and is absolutely free from 
any danger of short-circuiting any other machine or storage bat- 
ter}^ on the same circuit, it may be started while connected to the 
circuit, but not otherwise. If there are a large number of lamps 
connected to the circuit, the field magnetism and voltage might 
not be able to " build up " until the line is disconnected an 
instant. 

If one dynamo is to be connected to another, or to a circuit 
having other dynamos or a storage battery working upon it, the 
greatest care should be taken. This coupling together of 
dynamos can be done perfectly, however, if the correct method is 
followed, but is likely to cause serious trouble if any mistake is 
made. 



82 HANDBOOK ON ENGINEERING. 



SWITCHING DYNAMOS INTO CIRCUIT. 

Two Of more machines are often connected to a common cir-, 
cuit. This is especially the case in large buildings where tlie 
number of lamps required to be fed varies so much that one 
dynamo may be sufficient for certain hours, but two, three or 
more machines may be required at other times. The various 
ways in which this is done depending upon the character of the 
machines and of the circuit and the precautions necessary in 
each case make this a most important and interesting subject, 
which requires careful consideration. 

Dynamos may be connected together either in parallel (mul- 
tiple arc) or in series. 

DYNAflOS IN PARALLEL. 

In this case the + terminals are connected together or to the 
same line, and the — terminals are connected together or to the 
other line. The currents (i. e. amperes) of the machines are 
thereby added, but the e.m.f. (volts) are not increased. 
The chief condition for the running of dynamos in parallel is 
that their voltages shall be equal, but their current capacities 
may be different. For example: A dynamo producing 10 
amperes may be connected to another generating 100 amperes, 
provided the voltages agree. Parallel working is, therefore, 
suited to constant potential circuits. A dynamo to be connected 
in parallel with others or with a storage battery, must first be 
brought up to its proper speed, e.m.f., and other working con- 
ditions, otherwise, it will short-circuit the system, and probably 
burn out its armature. Its field magnetism must, therefore, be at 
full strength, owing to the fact that it generates no e.m.f. with 
no field magnetism. Hence, it is well to find whether the pole 
pieces are strongly magnetized by testing them with a piece of 



HANDBOOK ON ENGINEERING. 83 

iron, and to make sure of the proper working of the machine in 
all other respects before connecting the armature to the circuit. 
It is a common accident for the field-circuit to be open at some 
point, and thus cause very serious results. In fact, a dynamo 
should not be connected to a circuit in parallel with others until 
its voltage has been tested and found to be equal to, or slightly 
(not over 1 or 2 per cent) greater than that of the circuit. If the 
voltage of the dynamo is less than that of the circuit, the current 
will flow back into the dynamo and cause it to be run as a motor. 
The direction of rotation is the same, however, if it is shunt- 
wound, and no great harm results from a slight difference of 
potential. But a compound-wound machine requires more careful 
handling. 

DIRECTIONS FOR RUNNING DYNAflOS AND flOTORS. 

In the case of a machine which has not been run before, or 
has been changed in any way, it is of course wise to watch it 
closely at first. It is also well to give the bearings of a new 
machine plenty of oil at first, but not enough to run on the arma- 
ture, commutator or any part that would be injured by it, and 
to run the belt rather slack until the bearings and belt have got- 
ten into easy working condition. If possible, a new machine 
should be run without load or with a light one for an hour or 
two, or several hours in the case of a large machine ; and it is 
always wrong to start a new machine with its full load, or even 
a large fraction of it. 

This is true even if the machine has been fully tested by its 
manufacturer and is in perfect condition, because there may be 
some fault in setting it up, or some other circumstance which 
would cause trouble. All machinery requires some adjust- 
ment and care for a certain time to get it into smooth working 
order. 



84 HANDBOOK ON ENGINEERING. 

When this condition is reached, the only attention required 
is to supply oil when needed, keep the machine clean and see 
that it is not overloaded. A dynamo requires that its voltage or 
current should be observed and regulated if it varies. The per- 
son in charge should always be ready and sure to detect the 
beginning of any trouble, such as sparking, the heating of any 
part of the machine, noise, abnormally high or low speed, etc., 
before any injury is caused, and to overcome it by following 
directions given elsewhere. Those directions should be pretty 
thoroughly committed to mind, in order to facilitate the prompt 
detection and remed}' of any trouble when it suddenly occurs, as 
is apt to be the case. If possible, the machine should be shut 
down instantly when any trouble or indication of one appears, 
in order to avoid injury and give time for examination. 

Keep all tools or pieces of iron or steel away from the machine 
while running, as they might be drawn in by the magnetism, and 
perhaps get between the armature and pole-pieces and ruin the 
machine. For this reason, use a zinc, brass or copper oil-can 
instead of iron or " tin " (tinned iron). 

Particular attention and care should be given to the commu- 
tator and brushes to see that the former keeps perfectly smooth 
and that the latter are in proper adjustment. (See Sparking.) 

Never lift a brush while the machine is delivering current, 
unless there are one or more other brushes on the same side to 
carry the current, as the spark might make a bad burnt spot on 
the commutator. 

Touch the bearings and tield-coils occasionally to see that 
they are not hot. To determine whether the armature is running 
hot, place the hand in the current of air thrown out from it by 
centrifugal force. 

Special care should be observed by any one who runs a dynamo 
or motor to avoid overloadhuj it, booauso this is the cause of most 
of the trou])les which occur. 



HANDBOOK ON ENGINEERING. Sb 

PERSONAL SAFETY. 

Never allow the body to form part of a circuit. Wliile band- 
ling a conductor, a second contact may be made accidentally 
through the feet, hands, knees, or other part of body in some 
peculiar and unexpected manner. For example, men have been 
killed because they touched a "live" wire while standing or 
sitting upon a conducting body. 

Rubber gloves or rubber shoes, or both, should be used in 
handling circuits of over 500 volts. The safest plan is not to 
touch any conductor while the current is on, and it should be 
remembered that the current may be present when not expected, 
due- to an accidental contact with some other wire or to a change 
of connections. Tools, with insulated handles, or a dry stick of 
wood, should be used instead of the bare hand. 

The rule to use only one hand when handling dangerous elec- 
trical conductors or apparatus is a very good one, because it 
avoids the chance, which is very great, of making contacts with 
both hands and getting the full current right through the body. 
This rule is often made still more definite by saying, " Keep one 
hand in your pocket," in order to make sure not to use it. The 
above precautious are often totally disregarded, particularly by 
those who have become careless by familiarity with dangerous 
currents. The result of this has been that almost all the persons 
accidentally killed by electricity have been experienced electric 
linemen or stationmen. 



86 HANDBOOK ON ENGINEP^RING. 



CHAPTER VIII. 

WHY COHMUTATOR BRUSHES SPARK AND WHY THEY DO 
NOT SPARK. 

I mig-ht give a long list of reasons why commutator brushes 
spark, and why they do not spark, but by such a procedure no 
light would be thrown on the subject, because the reasons would 
not be understood unless fully explained. I therefore propose to 
explain the subject and let the reader tabulate the reasons after 
digesting the explanation of the principles involved. 

Whenever an electric current is interrupted, a spark is pro- 
duced, and it makes no difference how the current is generated, 
or what kind of a conductor it is flowing through. To break 
a current without a spark is not a possibility ; hence, if we 
desire to open a circuit without producing a spark, the only 
way to accomplish the result is by killing the current before 
the circuit is opened. The brushes resting on the commutator 
of a motor or a generator have to transmit to the armature 
and take av/ay from it the current that is generated, in the case 
of a generator, or the current that drives the machine in the case 
of a motor. If the brushes were made so narrow that they 
could only make contact with one commutator segment at a time, 
it would be impossible to run the machine without producing 
very destructive sparks. To fulfill these conditions, the brushes 
would have to be very thin, and the insulating separation between 
the segments rather wide, so that the width of the latter would 
be more than the width of the end of the brush. With these 
proportions, the brush could rest entirely upon an insulating strip, 
and would not touch the adjoining segments. Commutators, how- 
ever, are not made in this way. The insulation between the seg- 



HANDBOOK ON ENGINEERING. 87 

meuts is narrow, aud the brushes are wide enough to be always 
in contact with two segments, and part of the time with three, 
while in some machines the brushes cover three segments, and 
part of the time make contact with four. Now, suppose that the 
proportions are such that during most of the time the brush only 
touches two segments, as, for example, the proportions shown in 
Fig. 1. With these proportions, it will be seen, by reflecting 
upon the subject, that so long as there are two segments in con- 
tact with each brush, it is a possibility for the current to be 
diverted through one of them only. Now, suppose that at the 
instant when the forward segment is passing from under the brush, 
all the current flows through the rear segment ; then it is quite 
evident that the first-named segment will break awa}^ from contact 
with the brush without making a spark, for there will be no 
current flowing from it to the brush, hence, no current to inter- 
rupt ; and there can be no spark unless there is an interruption 
of a current. 

All the foregfoing- is self-evident, but it will be suggested 
that although the brush can break away from the front segment 
without producing a spark, it cannot do the same thing with the 
rear segment, for all the current is flowing through this one. 
This way of looking at the matter is not correct, however, for 
while it is true that when the forward segment passed from under 
the brush all the current was flowing through the rear segment, 
it is not true that the current continues to follow this path. 
As soon as the front segment passes from under the brush, the 
rear one becomes the forward segment, and while it is advanc- 
ing to the point where it must pass from under the briish, 
the current can be transferred to the next segment back of it 
which now plays the part of rear segment. Thus we see that to 
be able to run a machine without producing sparks at the com- 
mutator, all we have to do is to provide means whereby the current 
is transferred from one segment to the one back of it as the 



88 ' HANDBOOK ON ENGINEERING. 

I 

commutator revolves, so that wlieii the segments pass from imder - 
the brush there is no current flowing through them. This result 
is accomplished more or less perfectly in all machines, made by 
responsible firms. There are machines on the market that have 
been designed by men that are not well enough posted in the 
principles of electrical science to obtain proper proportions, and 
these are not proportioned so as to shift the current from the for- 
ward to the rear segment as fast as the machine revolves ; such 
machines always produce more or less serious sparking. 

If a machine i» accurately made and the armature coils and 
commutator segments are properly spaced and sufficient in num- 
ber, it is possible to get the brushes so there will be little or no 
spark at a given load ; but if the current strength be increased or 
reduced, the sparks will appear, and the more the current is 
changed the larger the sparks will ]ie, the increasing current 
producing the greatest sparking. 

The way ii^ which the current is shifted from the front to the 
rear segment I will explain in connection with Fig. 1. In this 
figure, A represents a portion of the core of a ring armature. 
The shaft upon which it is mounted is shown at 1), and F N are 
the corners of the poles between which it rotates. The small 
blocks C represent a portion of the commutator segments, which 
we have placed outside of the armature, so as to make the diagram 
as simple as possible. For the same reason I have shown the 
armature coils as made of two turns of wire each. The line F F 
divides the space between the ends of the poles into two equal 
parts, and the line EE divides the armature into the two halves 
on whicli the direction of the induced currents is opposite. In 
all the coils to the right of line E E the currents are induced in 
a direction away from the shaft, and in all the coils to the left of 
line E E the currents flow toward the shaft, all of which is 
clearly indicated by the arrow heads placed upon the lines repre- 
senting the coils. The outline B represents the end of one of 



HANDBOOK ON ENCINEEKTNG = 



89 



the brushes, iiud from the direction iii which it is inclined it will 
be understood that the armature revolves in a direction counter to 
that of the hands of a clock. 

When the armature is in the position shown, the current Howl- 
ing in the coils to the right of line E E passes to segment />, and 




Fig. 1. 

thus reaches the brush, while the current flowing in the coils 
to the left of line E E reaches segment «, and through this 
passes to the brush. As the brush rests upon segments a and h^ 
the coil with which they connect is short-circuited, and there- 
fore a current can flow in it in any direction, or there may be 
no current. To be able to run without spark, or to obtain per- 



90 HANDBOOK ON ENGINEERING. ^ 

feet commutation, as it is called, the current in this short- 
circuited coil, when in the jjosition shown, should be zero, or 
nearly so. This coil, which is short-circuited by the brush, 
is called the commutated coil, or the coil undergoing com- 
mutation. It will be noticed that this commutated coil is in 
a position just forward of the line E E ; hence, the action of 
pole F will be to develop a current in it that will flow in 
the same direction as the current in the coils a,head of it, 
that is, in the coils to the left. Now if this current flowed 
through the brush, it would be in a direction contrary to that of 
the arrow at a; hence, it would act to check the current flowing 
from the front segment a to the brush, and would divert it through 
the commutated coil to the rear segment h. If the action of pole 
P upon the commutated coil is sufficiently vigorous, the current 
developed in it will be as strong as the current in the coils ahead 
of it, by the time the end of the segment is about to break away 
from the brush ; and this being the case, there will be no current 
from segment a to the brush, and consequently, no spark. If the 
action of jDole P is not strong enough, then there will be a small 
current from segment a to the brush when they separate, and as 
a result, a small spark. If the action of pole P on the commu- 
tated coil is too vigorous, then the current developed in it will be 
too great, and it will not only divert all the current coming from 
the forward coils, through the commutated coil to segment 6, but 
in addition will develop a local current that will circulate through 
"the end of the brush, and therefore, when the separation occurs, 
there will be a current flowing from the brush to the front seg- 
ment, and consequently, a spark. 

If the commutated coil were placed astride of line E E, the 
action of pole P upon it would be no greater than that of pole N, 
so that no current would be developed in it while undergoing com- 
mutation. The further the coil is in advance of line E, when 
short-circuited by the brush, the stronger the action of pole P 



HANDBOOK ON ENGINEERING. 91 

upon it; therefore, the strength of the current developed in the 
commutated coil can be increased by moving the brush further 
away from pole P. Hence, by trial, a point can be found where 
the current developed will be just sufficient for the purpose and 
no more. This is true, supposing the curreut developed by the 
armature to remain constant, but, if it varies, the current in the 
commutated coil will be either too great or too small. If, when 
the brushes are set, the armature is delivering a current of, say, 
twenty amperes, then the current flowing through the coils to 
the left of the brush will be ten amperes, and the current in 
the commutated coil will also be ten amperes. If the armature 
current increases to forty amperes, the current in the forward 
coils will be twent}^ amperes, and as that in the commutated coils 
will still be ten amperes, it will have only one-half the strength 
required for perfect commutation. In practice, however, it is 
found that if the commutator have a sufficient number of seg- 
ments, and the proportions of the machine are such that the line 
E E remains practically in the same position for all strengths of 
armature current, then, if the brushes are set so as to run spark- 
less with an average load, they will run so nearly sparkless with 
a heavy or light load as to make it difficult to detect the 
difference. 

Even when a machine is properly proportioned, the brushes 
may spark badly if they are not set in the proper position and 
with the ptoper tension. If the tension is not right, they will 
spark no matter where they are set. If the tension is too light, 
they will spark, because they will chatter and thus jump off the 
surface of the commutator. If the tension is too great, they will 
spark because they will cut the commutator, and then the latter 
will act as a file or grindstone and cut away particles from the 
brushes, and these will conduct the current from segment to seg- 
ment, as well as from the segment to the brush. Whenever a 
commutator is seen to be covered with fine sparks, some of which 



92 



HANDBOOK ON ENGINEERING. 



run all the way aroiiiKl the circle, it may be depended upon that^ 
the surface is rough, due in most cases to too much pressure on 
the brushes, and the remedy is to smooth it up and reduce the 
tension and set the brushes where they will run with the smallest 
spark. When the brushes begin to spark they rarely cure them- ; 
selves and the longer they are allowed to run with a heavy spark, 
the worse they will get. 




Fig. 2. 



Two-pole machines in which gauze brushes are used,* frequently 
give trouble on account of the tension being so great as to cause 
the brushes to cramp and be dragged along by the friction against 
the commutator surface. This action is illustrated in Fig. 2, in 
which the dotted lines show the end of the brush pulled forward 
by the friction against its end. Sometimes this occurs from using 
gauze brushes in brush-holders that were originally made to hold 
copper leaf brushes. As the gauze is not very elastic, if it gets 
a bend it does not come back to its original shape, hence in the 



HANDBOOK ON ENGINEERING. 93 

course of time it gets badly out of line. To remedy this difficulty, 
the best procedure is to place a strip of spring brass on top of 
the brush that will reach nearly to the end. Then unless the 
tension is entirely too great, it will not be pulled forward by the 
friction on the end. 

SPARKING AT COMMUTATOR. 

This is one of the most common troubles, the objection to it 
being that it wears, or may even destroy the commutator and 
brushes, and produces heat, which may injure the armature or 
bearings. Any machine having a commutator is liable to it, in- 
cluding practically all direct-current and some alternating-current 
machines. Alternating-current machines have continuous collect- 
ing rings which are not likely to spark, but self -exciting or com- 
pound-wound alternators require a supplementary continous- 
current commutator which may spark. This trouble can be 
prevented in most cases, however, by proper construction and care. 
Of all the troubles which may occur, sparking is the only one 
which is very different in the different types of machines. In 
some its occurrence is practically impossible. In others, it may 
result from a number of causes. The following cases of sparking 
apply to nearly all machines, and they cover closed-coil dynamos 
and morors completely. 

The very peculiar cases w^hich may arise in jjarticular types of 
open-coil armatures can only be reached by special directions 
for each. A certain amount of sparking occurs normally in 
most constant-current dynamos for arc-lighting, where it is not 
very objectionable, since they are designed to stand it and the 
current is small. 

Cause* — Armature carrying too much current, due to (a) 
overload (for example, too many lamps fed by dynamo, or too 
mucli mechanical work done by constant potential motor) ; a bad 
shoit-circuit, leak or ground on the line may also have the effect 



^^ HANDBOOK ON ENGINEERING. 

of overloading a dyuamo ; (b) excessive voltage ou a con- 
stant-potential circuit or excessive amperes on a constant- 
current circuit. In the case of a motor on a constant potential 
circuit, any friction, such as armature striking pole-pieces, or 
shaft not turning freely, will of course have the same effect as 
overload in producing excessive current. The armature of a 
motor on a constant-current circuit does not tend to heat more 
when overloaded, because the current and the heat it produces in 
the armature (C- i? ) are constant. In fact, the armature can 
be stopped with full current on without injury, except loss of 
ventilation . 

Symptom* — Whole armature becomes overheated, and belt 
very tight on tension side, and sometimes squeaks, due to 
slipping on pulley. Overload due to friction is detected by 
stopping machine and then turning it slowly by hand. (See 
" Heating of Bearings " and " Noise," Cause.) 

Remedy* — (e) Reduce the load or eliminate the short-circuit, 
leak or ground on the line ; (d) decrease the size of driving- 
pulley, or (e) increase the size of driven pulley ; (f ) decrease 
magnetic strength of the field in the case of a dynamo, or in- 
crease it in the case of a motor. If excess cf current cannot 
satisfactorily be overcome in any of the above ways, it will 
probably be necessary to change the machine or its winding. 
(Overload due to friction is eliminated as described under 
" Heating of Bearings " and " Noise.") 

If the starting or regulating box of a motor on a constant 
potential circuit has too little resistance, it will cause the 
motor to start too suddenly and spark badly at first. The 
only remedy is more resistance in the box. 

Cause* — Brushes not set at the neutral point. 

Symptom* — Sparking, varied by shifting the brushes with 
rocker-arm . 

Remedy* — Carefully shift brushes backwards or forwards 



HANDBOOK ON ENGINEERING. ^ 95 

until sparking is reduced to a minimum. This may be done 
by simply moving the rocker-arm. If only slightly out of posi- 
tion, heating alone may result, without disarrangement being 
bad enough to show sparking. If the brushes are not exactly 
opposite, or in a four-pole machine 90° apart, they should be 
made so, the proper points of contact being determined by 
counting the commutator-bars, or measuring with a string or 
paper. The brushes should also be carefully adjusted in line 
with each other. If one is ahead or behind the others, they 
may span too much of the commutator. 

The usual position for brushes in two-pole machines is 
opposite the spaces between the pole-pieces. If the brushes are 
set very far wrong, namely, half way toward the proper position 
for the other brush, it will -cause a dynamo to fail to generate, 
and a motor to fail to start. (See " Dynamo Fails to Gener- 
ate.") 

Cause. — Commutator rough, eccentric, or has one or more 
'' high bars " i3rojecting beyond the others, or one or more flat 
bars, commonly called "flats," or projecting mica, anyone of 
which causes brush to vibrate, or to be actually thrown out of 
contact with commutator. The effect of eccentricity may be 
produced by the shaft being loose in bearings while commutator is 
perfectly true on shaft. This will allow whole armature to 
chatter when running at full speed. Hard mica between the bars 
which does not wear as rapidly as the copper, will throw 
brushes off. 

Symptom* — Note whether there is a glaze or polish on the 
commutator, which shows smooth working ; touch revolving com- 
mutator with tip of finger-nail, and the least roughness is 
perceptible, or feel of brushes to see if there is any jar. If the 
machine runs at high-voltage (over 250), the commutator or 
brushes should be touched with a small stick or quill to avoid 
danger of shock. In the case of an eccentric commutator, careful 



9<> HANDBOOK ON P^NGINEERING. 

examiiiatiou shows a rise and fall of the brush when commutator 
turns slowly, or a chattering of brush when running fast. Some- 
times, by sighting in line with brush contact one can see clear 
daylight between commutator and brush, owing to brush jumping 
up and down. 

Remedy ♦ — Smooth the commutator with a line tile or line sand- 
paper, which should be applied by a block of wood which exactly 
fits the commutator (in latter case, be careful to remove any sand 
remaining afterward; and never use emery'). If bearing is loose, 
put in new one. If commutator is very rough or eccentric, the 
armature should be taken out and put in a lathe, and the com- 
mutator turned off. Large machines sometimes have a slide-rest 
attachment, so that the commutator can be turned off without 
removing the armature. This is clamped on the pillow-block 
after removing the rocker-arm. 

In turning' a- commutator in the lathe, a diamond-pointed tool 
should be used, this being better than either a round or square 
end. The tool should have a very sharp and smooth edge, and 
only an exceedingly fine cut should be taken off each time in 
order to avoid catching in or tearing the copper, which is very 
tough. The surface is then finished by applying a " dead 
smooth " file while the commutator revolves rapidly in the lathe. 
Any pai-ticles of copper should then be carefully removed from 
between the bars. 

In order to have the commutator wear smooth and work well, it 
is desirable to have the armature shaft move freely back and forth 
about -ji or J of an inch in the bearings. The position of the 
bearings, pulleys, collars, and shoulders on the shaft and of the 
machine with respect to the belt should be such as to cause this 
to take place of itself — except in the case of types of machines 
in which the pole-pieces surround the ends of the armature. It 
is desirable for the (romnuitator to have a dull glaze of a brown or 
bronze color. A very bright or scraped appearance does not 



HANDBOOK ON ENGINEERING. 97 

indicate the best condition. Sometimes a very little vaseline, or a 
drop of oil may be applied to a commutator which is rough. Too 
much oil is very bad, and causes the following trouble. 

Cause* — Brushes make poor contact with commutator. 

Symptom, — Close examination shows that brushes touch only 
at one corner, or only in front or behind, or there is dirt on sur- 
face of contact. Sometimes, owing to the presence of too much 
oil or from other cause, the brushes and commutator become very 
dirty and covered with smut. They should then be carefully 
cleaned by wiping with oily rag or benzine, or by other means. 

Occasionally a " glass-hard " carbon brush is met with. It 
is incapable of wearing to a good seat or contact and will only 
touch in one or two points, and should be discarded. 

Remedy* — File, bend, adjust or clean brushes until they rest 
evenly on commutator, with considerable surface of contact and 
with sure but light pressure. Copper brushes require a regular 
brush-jig. Carbon brushes may be fitted perfectly by drawing a 
strip of sand-jDaper back and forth between them and the com- 
mutator while they are pressing down, which cuts them to the 
shape of the commutator. A band of sand-paper may be pasted 
or tied around the commutator, and if the armature is then slowly 
revolved by hand or by power, and the brushes are pressed upon 
it, they will be very effectively, rapidly and perfectly shai:)ed to 
the commutator. 

It sometimes happens that the brushes make poor contact, 
because the brush-holders do not turn or work freely. . 

Cause* — Short-circuited coil in armature or reversed coil. 

Symptom* — A motor will draw excessive current, even when 
running free without load. A dynamo will require considerable 
power even without any load. (For reversed coil, see " Heating 
of Armature.") 

The shoft-cifcuited coil is heated much more than the others, 
and is very apt to be burnt out entirely ; therefore, stop machine 

7 



98 HANDBOOK ON ENGINEERING. 

immediately. If necessary to run machine to locate the short- 
circuit, one or two minutes is long enough, but it may be re- 
peated until the short-circuited coil is found by feeling the 
armature all over. 

An iron screw-driver or other tool held between the field- 
magnates near the revolving armature vibrates very perceptibly 
as the short-circuited coil passes. Almost any armature, par- 
ticularly one with teeth, will cause a slight but rapid vibration of 
a piece of iron held near it, but a short-circuit produces a 
much stonger effect only once per revolution. Be very careful 
not to let the piece of iron be drawn in and jam the arma- 
ture. 

The current pulsates and torque is unequal at different parts 
of a revolution, these being particularly noticeable when arma- 
ture turns rather slowly. If a large portion of the armature is 
short-circuited, the heating is distributed and harder to locate. 
In this case a motor runs very slowly, giving little power, but 
having full-field magnetism. A short-circuited coil can also be 
detected by the drop-of -potential method. 

Remedy. — A short-circuit is often caused by a piece of solder 
or other metal getting between the commutator-bars or their con- 
nections with the armature, and sometimes the insulation between 
or at the ends of these bars is bridged over by a particle of metal. 
In any such case the trouble is easily found and corrected. If, 
however, the short-circuit is in the coil itself, the only real cure is 
to rewind the coil. 

One or more " grounds " in the armature may produce effects 
similar to those arising from a short-circuit. 

Cause* — Broken circuit in armature. 

Symptom* — Commutator flashes violently while running, and 
commutator-bar nearest the break is badly cut and burnt ; but in 
this case no particular armature coil will be heated, as in the last 
case and tlie flashing will be very much worse, even when turn- 



HANDBOOK ON ENGINEERING. 99 

ing slowly. This trouble, which might also be confouuded 
with a bad case of " high-bar" or eccentricity in commutator 
(sparking), is distinguished from it by slowly turning the arma- 
ture, when violent flashing will continue if circuit is broken, 
but not with eccentric commutator or even with " high bar," 
unless the latter is very bad, in which case it is easily felt or 
seen. A very bad contact would have almost the same effect as 
a break in the circuit. 

Remedy* — The trouble is often found where the armature 
wires connect with the commutator and not in the coil itself, and 
the break may be repaired or the loose wire may be resoldered or 
screwed back in place. If the trouble is due to a broken com- 
mutator connection and it cannot be fixed, then connect the dis- 
connected bar to the next by solder, or '^ stagger " the brushes ; 
that is, put one a little forward and the other back so as to bridge 
over the break. If the break is in the coil itself, rewinding is 
generally the only cure. But this may be remedied temporarily 
by connecting together by wire or solder the two commutator- 
bars or coil terminals between which the break exists. It is only 
in an emergency that armature coils should be cut out of commu- 
tator bars connected together, or other makeshifts resorted to, 
but it sometimes avoids a very undesirable stoppage. A very 
rough but quick and simple way to connect two commutator-bars 
is to hammer or otherwise force the coppers together across the 
mica insulation at the end of the commutator. This should be 
avoided if possible, but if it has to be done in an emergency, it 
can afterwards be picked out and smoothed over. In carrying 
out any of these methods, care should be taken not to short-circuit 
any other armature coil which would cause sparking. 

Cause* — Ground in Armature. 

Symptom* — Two " grounds " (accidental connections between 
the conductors on the armature and its iron core, or the shaft or 
spider) would have practically the same effect as a short-circuit, 

L.ofC. 



100 HANDBOOK ON ENGINEERING. 

and would be treated iu the same way. A single ground would 
have little or no effect, provided the circuit is not intentionally or 
accidentally grounded at some other point. On an electric rail- 
way (" trolley "), or other circuit which employs the earth as the 
return conductor, one or more grounds in the armature would 
allow the current to pass directly through them, and would cause 
the motor to spark and have a very variable torque at different 
parts of a revolution. 

Remedy* — A ground is detected by testing with magneto bell. 
Another way to locate it is to wrap a wire around the commutator 
so as to make connection with all of the bars, and then connect 
a source of current to this wire and to the armature core (by 
pressing a wire upon the latter). The current will then flow from 
the armature conductors through the ground connection to the 
core, and the magnetic effect of the armature winding will be 
localized at the point where the ground is. This point is then 
found by the indications of a compass-needle when slowly moved 
around the surface of the armature. The current may be 
obtained from a storage-battery or from the circuit, but then it 
should be regulated by lamps or a resistance box, so as not to 
exceed the normal armature current. Sometimes the ground 
may be in a place where it can be corrected without much 
trouble, but usually the j^articular coil, and often others have to be 
rewound. A ground will be produced if the insulation is punc- 
tured by a spark of static electricity, which may be generated by 
the friction of the belt ; in fact, a belt usually gives off electric 
sparks while running. If the frame of the machine is connected 
to the ground, the static charge will pass off to the ground, but 
this grounding is not generally considered allowable. The frame 
may be connected to the ground through a Geissler tube, a wet 
thread, a heavy pencil-mark on apiece of unglazed porcelain, or 
otlier very liigli resistance which will carry off a static charge 
that is of very high potential and almost infinitesimal quantity, but 



HANDBOOK ON ENC4INEEK1N(4 . 101 

will not permit the passage of any considera))le current, which 
might cause trouble. 

Cause* — Weak field-magnetism. 

Symptom* — ^ny considerable vibration is almost sure to pro- 
duce sparking, of which it is a common cause. This sparking 
may be reduced by increasing the pressure of the brushes on the 
commutator, but the vibration itself should be overcome by the 
remedies referred to above. 

Cause* — Chatter of Brushes. The commutator sometimes 
becomes sticky when carbon brushes are used, causing friction, 
which throws the brushes into rapid vibration as the commutator 
revolves, similarly to the action of a violin-bow. 

Symptom* — Slight tingling or jarring is felt in brushes. 

Remedy. — Clean commutator and oil slightly. This stops it 
at once. 

HEATING IN DYNAflO OR HOTOR 

General Instructions* — The degree of heat that is injurious or 
objectionable in any part of a dynamo or motor is easily deter- 
mined by feeling the various parts. If the heat is bearable for 
a few moments, it is entirely harmless. But if the heat is un- 
bearable for more than a few seconds, the safe limit of tempera- 
ture has been passed, except in the case of commutators in which 
solder is not used ; and it should be reduced in some of the ways 
that are given below. In testing with the hand, allowance should 
always be made for the fact that bare metal feels much hotter 
than cotton, etc. If the heat has become so great as to produce 
an odor of smoke, the safe limit has been far exceeded and the 
current should be shut off and the machine stopped immediately, 
as this indicates a serious trouble, such as a short-circuited coil or 
a tight bearing. The machine should not again be started until 
the cause of the trouble has been found and positively overcome. 
Of course neither water nor ice should ever be used to cool elec- 



102 HANDBOOK ON ENGINEERING. 

trical machinery, except possibly the bearings of hirge nitichiues, 
where it can be applied without danger of wetting the other 
parts. 

Feeling for heat will answer in ordinary cases, but of course, 
the sensitiveness of the hand differs, and it makes a very great 
difference whether the surface is a good or bad conductor of heat. 
The back of the hand is more sensitive and less variable than the 
palm for this test. But for accurate results, a thermometer 
should be applied and covered with waste or cloth to keep in 
the heat. In proper working, the temperature of no parts of the 
machine should rise more than 45° C. or 81° F above the temper- 
ature of the surrounding air. If the actual temperature of the 
machine is near the boiling point, 100° C. or 212° F., it is seri- 
ously high. 

It is very important in all cases of heating to locate correctly 
the source of heat in the exact part in which it is produced. It 
is a common mistake to suppose that any i3art of a machine which 
is found to be hot is the seat of the trouble. A hot bearing may 
cause the armature or commutator to heat or vice versa. In 
every case, all parts of the machine should be felt to find which 
is the hottest, since heat generated in one part is rapidly diffused 
throughout the entire machine. It is generally much surer and 
easier in the end to make observations for heating by starting 
with the whole machine perfectly cool, which is done by letting it 
stand for one or more hours or over night, before making the 
examination. When ready to try it, run it fast for three to five 
minutes, with the field magnates charged ; then stop, and feel all 
parts immediately. The heat will be found in the right place, as 
it will not have had time to diffuse from the heated to the cool 
parts of the machine. Whereas, after the machine has run some 
time, any heating effect will spread until all parts are equal in 
temperature, and it will then be almost impossible to locate the 
trouble. 



HANDBOOK ON ENGINEERING. 103 

Excessive heating of commutator, armature, field magnates, or 
bearings may occur in any type of dynamo or motor, but it can 
almost always be avoided by proper care and working conditions. 

THE EFFECT OF THE DISPLACEMENT OF THE ARMATURE. 

After an electric generator or motor has been in use for 
several years it is liable, like other machines, to begin to act 
badly. It is then examined, and if anything is noticed that is not 
what it should be in appearance, this particular thing is assumed 
to be the cause of all the trouble. Sometimes the conclusion may 
be correct, but very often it is not. If a machine is old, it is 
more than likely the shaft will be found out of center, and if this 
fact is discovered at a time when things are not working as they 
should, it is taken for granted this is the cause of the trouble. 
What is true of shafts out of the center is true of several other 
things that are liable to get out of place. For the present it will 
be sufficient to investigate just what effect the displacement of 
the shaft can have ; then if the trouble with a machine so afflicted 
is not in the category of shaft disorders, we will know that we 
must seek further for the cause of the complaint. 

Fi§;. \ illustrates an armature of a two-pole machine which is 
out of center in one direction, and Fig. 2 shows another two-pole 
armature out of center in a direction of right angles to that 
shown in the first figure. The condition shown in Fig. 1 could 
be produced by a heavy armature running in rather light bear- 
ings for several years, and the side displacement of Fig. 2 could 
be produced by the tension of an extra tight belt. The mechan- 
ical effect of both these conditions would be to increase the pres- 
sure on the bearings, as the part a of the armature would be 
drawn toward the poles of the field with greater force than the 
opposite side. The downward pull, due to the attraction of the 
magnetism, would be greater in Fig. 1 than the side pull in Fig. 



104 



HANDBOOK ON ENGINEERING. 



2, supposing both armatures and fields to be the same in both 
cases, and the displacement of the shafts equal. This difference 
is due to the fact that in Fig. 1 the magnetism of both poles is 
concentrated at the lower corners on account of the shorter air 
gap ; hence, both sides pull much harder on the lower side. In 
Fig. 2, the pull of the ^pole is greater than that of the other, 
simply because in the latter the magnetism is more dispersed, but 
the difference in the density on the two sides will not be very 
great. If the bearings of a machine, with the armature dis- 
placed, as indicated, have shown any signs of cutting, or if the}' 




Fisf. 1. 



Fig. 2. 



run unusually warm, their condition will be improved l)y putting 
in new bearings that will bring the shaft central. 

If the armature is of the drum tyjDe, the displacement of the 
shaft will have no effect upon it electrically. This is owing to the 
fact that all the armature coils are wound from one side of 
the core to the other, and, therefore, at all times, every 
coil has one side under the influence of one pole and the other 
side under the influence of the opposite pole, and if one 
side is acted upon strongly by one pole, it will be acted 
upon feebly by the other. If the armature is of the ring type, 
then the displacement of the shaft will affect it electrically, for 
in a ring armature, the coils on one side are acted upon by 



HANDBOOK ON ENGINEERING. 105 

the pole on that side, only, and as the magnetic lield from 
one pole will be stronger than that from the other (that is, 
considering the action upon equal halves of the armature), the 
voltage developed in the coils on one side of the armature will be 
greater than that developed on the other side. In Fig 1 if the 
brushes h b could be j^laced on the vertical diameter, as shown, 
the electrical action would not be interfered with, for on each 
side of the vertical line the magnetic action would be the same. 
But the reaction of the magnetism developed by the armature 
current twists the magnetism around, so that the brushes have to 
be rotated around some distance from the vertical line ; therefore, 
even in the case of Fig. 1, the electrical balance will be disturbed 
if the armature is of the ring type. 

The effect of the disturbance of the electrical balance will be 
that the brushes will spark badly, because the voltage of the cur- 
rent generated on one side of the armature will be greater than 
than that of the current on the other side. Hence, when these 
two currents meet at the brushes, the strong one will tend to drive 
the weak one backward. If, while the armature is out of center, 
we wish to adjust the brushes so as to get rid of the excessive 
sparking, all we have to do is to set them to the right of the cen- 
ter line, as in Fig. 2, so that the wire on the left side will cover a 
greater portion of the circumference than the right ; or, what is 
the same thing, so there will be more commutator segments be- 
tween the brushes on the left side than on the right. In this way 
the voltages of the two armature currents can be equalized and 
the sparking can be reduced to the normal amount, or nearly so. 

In a multipolar machine, the displacement of the armature 
will have the same effect mechanically as in the two-pole type ; 
that is, it will increase the pressure on the bearings and prob- 
ably cause them to cut, or at least to run warmer than they should. 
The effect produced upon the electrical action will depend upon 
the way in which the armature is wound ; or, more properly 



106 HANDBOOK ON ENGINEERTNCJ . 

speaking, upon the way in which the anuatuie coils are con- 
nected with each other and with the comnintator segments. As 
was explained in articles on construction of electrical machines, 
multipolar armatures are connected in two different ways, one of 
which is called the wave or series winding, and the other the lap 
or parallel winding. In the first named type of winding, the ends 
of all the coils on the armature are connected with each other and 
with the commutator segments in such a manner that there arc 
only two paths through the wire for the current ; therefore, these 
two armature currents pass under all the poles and the voltage of 
each current is the combined effect of all the poles. From this 
very fact, it can be clearly seen that it makes no difference what 
the distance between the several poles and armature may be, for 
if some are nearer than the others, the only effect will be that 
these poles will not develop their share of the total voltage, but 
whatever their action may be, it will be the same on the coils in 
both circuits. 

When a multipolar armature is connected so as to form a 
parallel or lap winding, then the connections between the coil 
ends, and between these ends and the commutator segments, are 
such that as many paths are provided for the current as there are 
poles, and each one of these paths is located under one pole, and 
as a consequence, the voltage developed in it is proportional to 
the action of this pole. The diagram 3 illustrates a six-pole 
armature with the ends of the field poles, and the arrows a a, bb, 
c c, indicate the six separate divisions of the coils in which the 
branch currents are developed. Now, it can be clearly seen that 
as the armature is nearer to the lower j^oles than to any of the 
others, the action of these will be the strongest. Hence, the cur- 
rents a a will be stronger than the others and will have a higher 
voltage. These two currents will be taken off the commutator by 
the brushes at the lower corners. These same brushes also take 
off the currents developed by the action of the side poles, and 



HANDBOOK ON ENGINEERING. 



107 



which are indicated by the side arrows h c. These last two cur- 
rents will be weaker and of lower voltage than the a a currents, 
hence, the latter will try to crowd them back, and thus sparks 
will be produced at these brushes. 

The two upper currents are weaker than the side ones and 
their voltage is also lower, so that, the current returning to the 




Fig. 3. 

commutator through the brushes at the upper corners, will not 
divide equally, but the larger portion will be drawn into the coils 
on the side ; and as the upper coils will have to fight to hold their 
own, so to speak, there will be a disturbance of the balance that 
is required for smooth running. The result will be heavy spark- 
ing at these brushes. If these four brushes were shifted down- 
ward, the lower ones being moved more than the upper ones, 
points could be found where the sparking would disappear. This 



108 HANDBOOK ON ENGINEERING. 

readjustment of the brushes would be the same thiug, for a multi- 
polar machine, as the shifting to one side, as explained in con- 
nection with the action of a two-pole ring wound armature. 
Multipolar machines, however, are seldom made so that the 
brushes can be moved individually, so we cannot count on correct- 
ing the trouble temporarily in this way. In the great majority of 
cases, if the brushes of a multipolar machine spark on account of 
the armature being out of center, the only cure is to reset the 
bearings, if they are adjustable, and if they are not, to put in 
new ones. 

In the two-pole machines, we have seen that if the armature 
is of the drum type, the action of the brushes will not be affected 
by the displacement of the shaft, and this will also be the case in 
a multipolar machine if the armature is wave, or series wound. 
From this it will be inferred that there is a similarity between the 
two-pole drum winding and the multipolar wave winding, and 
such is really the case. The multipolar lap winding is the coun- 
terpart of the two-pole ring winding, and in fact, a ring wound 
armature will work perfectly" in a machine with any number of 
poles, provided we place upon the commutator as man}^ brushes 
as there are poles. If we made a ring armature and provided a 
number of different fields into which it would fit jDroperly, one 
being two-pole, one four-pole, one six-pole, one eight-pole, and 
the others of greater number of poles ; then, if each machine had 
as many brushes as poles, and these were set in the proper posi- 
tion, the armature would run as well in one as in the other, with- 
out requiring any changes in the connections between the arma- 
ture coils and the commutator. In fact, all we would have to do 
would be to remove it from one machine and place it on the other, 
and it would be ready to run. 

The regulat* ring winding is not used very often for multipolar 
machines, owing to the fact that the coils have to be wound in 
place, and on that account are not so mechanical in appearance, 



HANDBOOK ON ENGINEERING. 109 

and are more expensive to make. The former coils used almost 
universally for multipolar armatures, have both sides on the outer 
surface of the core, and on that account, when they are connected 
into a lap, or wave winding, they will not operate perfectly with 
a number of poles different from that for which they are con- 
nected, but they will run, although imperfectly, with any number 
of poles. From this it will be seen that if we have two generators 
of four and six poles respectively, both using armatures of the 
same diameter, and both lap wound, if one armature gives out we 
can use the armature of the other machine as a makeshift, but it 
will not give as good results as in its own field. An armature 
with a wave winding cannot be used except with a field of the 
number of poles for which it is wound. 

As sometimes it may be advantageous to change an armature 
from one machine to another while repairs are being made, pro- 
vided the dimensions of the machine are the same, it is desirable 
to know how to determine whether the winding is wave or lap 
connected. You cannot tell from the general appearance of the 
armature, because both are wound with formed coils, but if we 
examine the two ends of the armature, we will find that with the 
lap winding the coils bend toward the same side after leaving the 
grooves, while with the wave winding, they bend in opposite 
directions. To make this clearer, suppose we are standing at the 
side of the machine so we can see both ends of the armature ; if 
the coils on the commutator end bend down toward the floor, the 
ends will bend up toward the ceiling at the i3ulley end, if the 
connection is wave, and they will bend down, the same as at the 
commutator end, if the connection is lap. Sometimes the ends 
of the coils at the pulley end of the armature cannot be seen, but 
in such cases we can determine the type of connection if we can 
find out whether the connections from the coils to the commutator 
run in the same direction as the coils, or opj^osite to it. If the 
connections and the coil ends run in the same direction, the con- 



110 HANDBOOK ON ENGINEERING. 

nection is for lap winding, and if they run in opposite directions, 
the connection is for wave winding. If there are only two sets of 
brushes on the commutator, the armature is wave wound. If the 
armature is wave wound and there are as many brushes as poles, 
we will be able to remove all but two sets without making any 
material difference in the running of the machine ; but if the 
armature is lap wound, it will not run without the proper number 
of brushes. If a set of brushes is removed while the machine is 
in operation, a heavy flash will be produced with a lap winding, 
but with the wave winding there will be only a moderately large 
spark. Th^s it will be seen that there are several ways in which 
we can determine the type of winding. 

NOISE. 

Cause* — Vibration due to armature or pulley being out of 
balance. 

Symptom* — Strong vibration felt when the hand is placed 
upon the machine while it is running. Vibration changes greatly 
if speed is changed, and sometimes almost disappears at certain 
speeds. 

Remedy* — Armature or pulley must be perfectly balanced by 
securely attaching lead or other weight on the light side, or by 
drilling or filing away some of the metal on the heavy side. The 
easiest method of finding in which direction the armature is out 
of balance is to take it out and rest the shaft on two parallel and 
horizontal A-shaped metallic tracks sufficiently far apart to allow 
the armature to go between them. If the armature is then 
slowly rolled back and forth, the heavy side will tend to turn 
downward. The armature and pulley should always be balanced 
separately. An excess of weight on one side of the pulley and 
an equal excess of weight on the opposite side of the armature 
will not i)roduce a balance while running, though it does when 



HANDBOOK ON ENGINEERING. Ill 

standing still ; on the contrary, it will give the shaft a strong 
tendency to " wobble." A perfect balance is only obtained when 
the weights are directly opposite, i. e., in the same line perpen- 
dicular to the shaft. 

Cause* — Armature strikes or rubs against pole pieces. 

Symptom* — Easily detected by placing the ear near the pole 
pieces, or by examining armature to see if its surface is abraded 
at any point, or by examining each part of the space between 
armature and field, as armature is slowly revolved, to see if any 
portion of it touches, or is so close as to be likely to touch when 
the machine is running. Or turn armature by hand when no 
current is on, and note if it sticks at any point. It is unwise to 
have a clearance of less than J to J inch. 

Remedy* — Bind down any wire, or other part of the armature 
that may project abnormally, or file out the pole-pieces where the 
armature strikes, or center the armature so that there is a uni- 
form clearance between it and the pole-pieces at all points. 

Cause* — Shaft collar or shoulder, hub or edge of pulley or 
belt strikes or scrapes against bearings. 

Symptom* — Rattling noise, which stops when the shaft or 
pulley is pushed lengthwise away from one or the other of the 



Remedy* — Shift the collar or pulley, turn off the shoulder on 
the shaft, file or turn off the bearing, move the pulley on the 
shaft, or straighten the belt until there is no more striking and 
noise ceases. 

Cause* — Rattling due to looseness of screws, or other parts. 

Symptom* — Close examination of the bearings, shaft, pulley, 
screws, nuts, binding-posts, etc., are touching the machine while 
running or shaking its parts while standing still, show that some 
parts are loose. 

Remedy* — Tighten up the loose parts and be careful to keep 
them all in place and properly set up. It is very easy to guard 



112 HANDBOOK ON ENGINEERING. 

against the occurrence of this trouble, which is very common, by 
simply examining the various screws and other parts each day 
before the machine is started. Electrical machinery being usually 
high-speed, the parts are particularly liable to shake loose. A worn 
or poorly fitted bearing might allow the shaft to rattle and make 
a noise, in which case the bearing should be refitted or renewed. 

Cause* — Singing or hissing of brushes. This is usually 
occasioned by rough or sticky commutator, or by tips of brushes 
not being smooth, or the layers of a copper brush not being held 
together and in place. With carbon brushes, hissing will be 
caused by the use of carbon which is gritty or too hard. Ver- 
tical carbon brushes, or brushes inclined against the direction of 
rotation, are apt to squeak or sing. A new machine will some- 
times make noise from rough commutator, no matter how carefully 
it is turned off, because the difference in hardness between mica 
and copper causes the cut of the tool to vary, thus forming 
inequalities which are very minute, but enough to make noise. 
This can best be smoothed by running. 

Symptom* — Sound of high pitch, and easily located by plac- 
ing the ear near the commutator while it is running, and by lifting 
off the brushes one at a time, provided there are two or more on 
each side, so that the circuit is not opened. If there is no cur- 
rent, there is no objection to raising the brushes. 

Remedy* — Apply a very little oil or vaseline to the com- 
mutator with the finger or a rag. Adjust the brushes or smooth 
the commutator by turning, filing, or fine sand-paper, being 
careful to clean thoroughly afterwards. Carbon brushes are apt 
to squeak in starting up, or at slow speed. This decreases at 
full speed, and can usually be reduced by moistening the brush 
with oil, care being taken not to have any drops, or excess of oil. 
Shortening or lengthening the brushes sometimes stops the noise. 
Run the machine on open circuit until commutator and brushes 
are worn smooth. 



HANDBOOK ON ENGINEERING. 



113 



Table of Carrying: Capacity of Wires. — Below is a table which 
must be followed in placing interior conductors, showing the 
allowable carrying capacity of wires and cables of ninety-eight 
per cent conductivity, according to the standard adopted l^y the 
American Institute of Electrical Engineers. 





Table A. 


TABLE B. 






Rubber-Covered 


Weatherproof 






Wires. 


Wires. 




H. & S. G. 


Amperes. 


Amperes. 


Circular 3Jill 


18 


3 


5 


1,624 


16 


6 


8 


2,583 


14 


12 


16 


4,107 


12 


17 


23 


6,530 


10 


24 


32 


10,380 


8 


33 


46 


16,510 


6 


46 


65 


26,250 


5 


54 


77 


33,100 


4 


65 


92 


41,740 


3 


76 


110 


52,630 


2 


90 


131 


66,370 


1 


107 


156 


83,690 





127 


185 


105,500 


00 


150 


220 


133,100 


000 


177 


262 


167,800 


0000 


210 


312 


211,600 


Circular Mills. 








200,000 


200 


300 




300,000 


270 


400 




400,000 


330 


500 




500,000 


390 


590 




600,000 


450 


680 




700,000 


500 


760 




800,000 


550 


840 




900,000 


600 

8 


920 





114 HANDBOOK ON ENGINEERING. 





Table A. 


Table B. 




Rubber-Covered 


Weatherproof 




Wires. 


Wires. 


Circular Mills. 


Amperes. 


Amperes. 


1,000,000 


650 


1,000 


1,100,000 


690 


1,080 


1,200,000 


730 


1,150 


1,300,000 


770 


1,220 


1,400,000 


810 


1,290 


1,500,000 


850 


1,360 


1,600,000 


890 


1,430 


1,700,000 


940 


1,490 


1,800,000 


970 


1,550 


1,900,000 


1,010 


1,610 


2,000,000 


1,050 


1,670 



The lower limit is specified for rubber-covered wires to pre- 
vent gradual deterioration of the high insulations by the heat 
of the wires, but not from fear of igniting the insulation. The 
question of drop is not taken into consideration in the above 
tables. 

Insulation Resistance. — The wiring in any public building 
must test free from grounds ; i. e., the complete installation must 
have an insulation between conductors and between all conduc- 
tors and the ground (not including attachments, sockets, recep- 
tacles, etc.) of not less than the following: — 

Up to 



5 amperes, 


, 4,000,000 


Up to 200 


amperes, 100,000 


10 


2,000,000 


400 


" 25,000 


25 


800,000 


800 


" 25,000 


50 
.00 


400,000 
200,000 


'^ 1,600 


12,500 



All cutouts and safety devices in plsioe in the above. 
Where lamp sockets, receptacles and electroliers', etc., are con- 
nected, one-half of the above will be required. 



HANDBOOK ON ENGINEERING. 



115 



Soldering; Fluid. — ci. The following formula for soldering 
fluid is suggested : — 

Saturated solution of zinc chloride, 5 parts. 
Alcohol, 4 parts. 

Glycerine, 1 part. 

Bell or Other Wires* — a. Shall never be run in same duct 
with lighting or power wires. 

Table of Capacity of Wires* — 



6 
19 


la 

go 

< 

1,288 


1 

O 


CO 02 


i 

a 

< 


18 


1,624 






3 


17 


2,048 


... 






16 


2,583 






6 


15 


3,257 








14 


4,107 






12 


12 


6,530 






17 




9,016 




19 


21 




11,368 




18 


25 




14,336 




17 


30 




18,081 




16 


35 




22,799 




15 


40 




30,856 


19 


18 


50 




38,912 


19 


17 


60 


... 


49,077 


19 


16 


70 


... 


60,088 


37 


18 


85 




75,776 


37 


17 


100 


... 


99,064 


61 


18 


120 


... 


124,928 


61 


17 


145 




157,563 


61 


16 


170 



116 



HANDBOOK ON ENGINEERING. 



m 



6 


a 




^^i 




A3 


1^ 
*c5 


o 


|a3 


1 




< 


o 

5?; 


j» 




... 


198,677 


61 


15 


200 


... 


250,527 


61 


14 


235 


... 


296,387 


91 


15 


270 


... 


373,737 


91 


14 


320 


... 


413,639 


127 


15 


340 



When greater conducting area than that of B. & S. G. is re- 
quired, the conductor shall be stranded in a series of 7, 19, 37, 
61, 91 or 127 wires, as may be required; the strand consisting 
of one central wire, the remainder laid around it concentrically, 
each layer to be twisted in the opposite direction from the pre- 
ceding. 

TABLE SHOWING THE SIZE OF WIRE OF DIFFERENT METALS THAT 
WILL BE MELTED BY CURRENTS OF VARIOUS STRENGTHS. 



Strength 
of 


DIAMETER OE 


WIRE IN THOUSANDTHS OF AN INCH. 


/^iTt»T*rf^'n t' 














\J U.1 1 cixt 

in 
Amperes. 


Copper. 


Aluminum. 


Platinum. 


German 
Silver. 


Iron. 


Tin. 


1 


.002 


.003 


.003 


.003 


.005 


.007 


2 


.003 


.004 


.005 


.005 


.008 


.011 


3 


.004 


.005 


.007 


.007 


.010 


.015 


4 


.005 


.006 


.008 


.008 


.012 


.018 


5 


.006 


.008 


.010 


.010 


.014 


.021 


10 


.009 


.012 


.016 


.016 


.022 


.033 


15 


.013 


.016 


.020 


.020 


.028 


.044 


20 


.015 


.019 


.025 


.025 


.034 


.053 


25 


.018 


.022 


.029 


.029 


.040 


.062 


30 


.020 


.025 


.032 


.032 


.045 


.069 


35 


.022 


.028 


.036 


.036 


.050 


.077 


40 


.025 


.030 


.039 


.039 


.055 


.084 


50 


.027 


.033 


.042 


.042 


.059 


.091 


60 


.029 


.035 


.045 


.045 


.063 


.098 



HANDBOOK ON ENGINEERING. 



117 



CHAPTER IX. 

INSTRUCTIONS FOR INSTALLING AND OPERATING APPAR- 
ATUS FOR ARC LIGHTING, BRUSH SYSTEM. 

Theory of the brush arc gfeneraton — The Brush Arc Gen- 
erator is of the open coil type, the fundamental principle of which 
is illustrated in Fig. 1. Two pairs of coils, placed at right angles 




Fig. I. 



on an iron core, are rotated in a magnetic field. The horizontal 
coils represented in the diagram are producing their maximum 
electromotive force, while the pair of coils at right angles to them 
is generating practically no electromotive force. The brushes 
are placed on the segments of the four-part commutator, so as to 
collect only the current generated by the two horizontal coils. 
The other coils are open circuited, or completely cut out of the 
circuit. 



118 HANDBOOK ON ENGINEERING. 

Such a machine will generate curreut, continuous in direction, 
but fluctuating considerably in amount. These fluctuations will 
be diminished by the addition of more coils to the armature. 




Fig, 2 is a diagrammatic representation of an eight coil 
machine. The ends of coils diametrically opposite are connected 
as in the four-pole machine, but to avoid complications, these 
connections have been omitted on the diagram. In the eight coil 
machine, one psiir of coils, A\ A^, is generating maximum elec- 
tromotive force. At right angles to these coils, the coils C^ and 
C^ are generating no electromotive force. In intermediate 
l^ositions, the coils B^, &, D^, D^ are generating a useful electro- 
motive force, although one which is not so high as that generated 
by the coils A^ and A'^. 

In collecting the current from such an armature, the coils in 
the intermediate positions cannot be connected in parallel with 
the coils generating maximum electromotive force, because their 
electromotive force is lower. The pair of coils A^, A"^ can, how- 
ever, be placed in series and connected in series with the two pairs 



HANDBOOK ON ENGINEERING. 



119 



of coils jgi, B^ and 1)^,1)'^, which may be placed in parallel with 
each other, since they occupy similar positions in the magnetic 
field. 

The resistance of the coils in intermediate positions is, there- 
fore, halved, and the electromotive force is equal to the electro- 
motive force developed by one pair of coils. In the Brush Arc 
Generator a double commutator is used to automatically make 
these connections. 

In Fig» 3 this commutator is developed or spread out, and the 
coils are represented diagrammatically. With the brushes in the 
position shown, the current enters the brush P and the coil A^, 
which is placed in series with the coil J.^ in a similar part of the 
magnetic field. From the brush Q, the current is transferred to 
the second commutator, which it enters by the brush J?. This 
brush, m the position shown, rests on two segments, thus con- 
necting two pairs of coils in parallel. The current flowing 




Fig. 3. 



through these coils, B^, B^ and i)\ D^, leaves the machine by 
the brush S. The coils G^ and C^ which are generating no elec- 
tromotive force, are disconnected. 



120 



HANDBOOK ON ENGINEERING. 






The same arniugemeul 
is shown in Fig. 4, in 
wliich the coils have been 
^^ 1^ — '■ - H^ — i^ replaced by battery cells. 

H<^' c^ Althougfh the number 
of coils, and, therefore, 

D2 D. the number of commutator 

Yia A segments in larger Brush 

machines do not correspond 
with these diagrams, the principle of operation of the machine is, 
in every case, the same, and can be readily understood by reduc- 
ing it to these elementary forms. 

THE BRUSH MULTICIRCUIT DEVICE. 

The function of the Brush Multi-Circuit Device is to divide 
the load into several circuits, thus reducing the maximum poten- 
tial required and, consequently, the strain on the insulations. 
The operation of the device will be understood by reference to 
the following diagrams and explanations : — - 

Figs* J to 4 show that the potential of an eight coil machine is 
made up of the potential of one pair of coils, giving maximum 
electromotive force, and the potential of two other pairs in 
parallel, giving a lesser electromotive force. 

Fig. 3 is a development of the commutator of the Brush Arc 
Machine, showing how the potentials of the different coils are 
compounded. In this diagram the current takes the following- 
path : Brush P to coils ^4\ ^1^, brush Q to brush R to coils 
51, B^ and 7>\ i>^, in parallel, to brush S. 

Inasmuch as one pair of coils is always in series with two 
other pairs in parallel, it is immaterial whether the load is all 
placed between the terminals of the machine or divided between 
the various coils ; for example, instead of connecting all the 
lamps between the brushes P and /S, some may be connected be- 



HANDBOOK ON ENGINEERING. 



121 



tweeu brushes 1* aud S^ and the remainder between brushes li 
and Q. 

The arrangement will be clearly understood by reference to 
Figs. 5 and 6, in which the coils of the machine have been re- 
placed by battery cells. These diagrams show the arrangement 
of cells (coils) when the brushes occupy the position shown in 
Fig. o. The potential of the machine at this time is seen to be 
made np of the electromotive force of the pair of coils A^^ A-^ in 



I — X— X— X— X— X — X— X — X- 



+ 



HHt 



'hh 



'hi 



D2 D, 

Fig. 5- 



j^-hh 



series with the two j^airs of coils i^i, B^ and i)i, D^, "which are 
parallel. The pair of coils (7^, G^ is disconnected. 

With this arrangfement it is evident that, having a given 
number of lamps to install, they may be connected between the 
points P and S^ as in Fig. 5, or part of them may be connected 
between P and S and the remaining ones between R and Q, as in 
Fig. 6. Inasmuch as the potential between P and S (Fig. 5) is 
adequate to supply the total number of lamps installed in the cir- 
cuit, it is immaterial as to how the lamps are divided between P 
and S and R and Q (Fig. 6). If more lamps are installed be- 
tween P and >S' than are provided for by the potential generated 
by the cells (coils) connected between the points P and Q, the 



122 



HANDBOOK ON ENGINEERING. 



deficit will be made up by the potential generated between It 

and S. 



r 



X — X— X— X- 



,hM 



-X— X— >r— X — , 



^hh 



Inhh 



Da Di 

Fig. 6. 



In the Brush Multi-circuit Device, a number of switches are 
so arranged that lamps may be cut in or out of a divided circuit 
in the manner indicated. In the larger machines, the principle of 
operation is the same. 

BIPOLAR BRUSH ARC GENERATORS. 

Bipolar Brush Machines were built in eight sizes, ranging 
in capacity from 1 to 65 lamps of 2000 candle-power, and 2 to 

45 lamps of 1200 candle- 
power. (See table, page 
123.) 

Although now su- 
perseded by the larger 
multipolar machines, so 
^ many bipolar machines 
are still in use that I 
consider it advisable to 
publish the following instructions for operating and making 
such repairs as become necessary after the long service which 
thousands of these machines have undergone. 




HANDBOOK ON ENGINEERING. 



123 



|g||ig|ig|^g* 



I I^J^ISIIcUltcl 



SSI^ISlSl^lrol 



l§g! 



IS^f 



^^ -^ C) W *> M to 



-SS i 



1000-1500 
->cS o ^ M Acc'di'g'to 
gg g g g Resistance 

_^_____ ~ of Line. 



^O ^ M to VI 

•^*^ w- s- «- *,« 



gS g 



OO O M 



cisw ^ w 5 « w 



^^i 



M CJ « Ot 






"- ^ 



OQO !^ S^ O 00 



>S© «0 Oi 



5i -fe ^ -S£ 



00-a CS W lU 



S S ft 

«- K<^ So 



Amperes. 



Capacity in 
1200 C. P. 
Lamps. 



Capacity in 
2000 C. P. 
Lamps. 



Class No. 
of Machine. 



Diam. of 
Armature. 



H.P. 
Required 
at Pulley. 



Revs, per 
Minute. 




124 HANDBOOK ON ENGINEERING. 

The general construction of the bipolar machine is siiown in 
the diagram on page 123. Four field spools are provided, one pair 
to each side of the armature. The field cores are bolted to ver- 
tical yokes at each end of the machine, which also carry the 
bearings for the armature shaft. 

The machines should be set up in the manner described under 
Multipolar Generators on page 131. The wood base frame is 
fitted with belt tighteners, and anchor bolts and plates can be 
provided for the larger sizes, if ordered. To operate satisfac- 
torily, %he machines must be kept perfectly clean, the oil cups 
well filled and the commutator surfaces smooth. (See page 
140.) 

The armature ^'ith its shaft may be readily removed after 
unscrewing the bolts and lifting the caps from the bearings at 
each end. 

Each coil or bobbin on the armature is wound independently, 
and may be rewound without disturbing any other part of the 
armature. The inside ends of coils diametrically opposite are 
connected together, while their opposite ends are connected by 
means of wires running through the hollow shaft to opposite 
segments of the commutator.* Thus each pair of coils has a 
separate pair of segments lying in the same radial plane as tlie 
two coils. 

The pairs of segments are grouped in sets of two to preserve 
the continuity of the current. Each ring represents two pairs of 
coils 90° apart. 

Proper connections are made by having separate brushes for 
each commutator ring consisting of two pairs of segments. Thus 
in an eight coil machine, the lower brush on one commutator ring 
is connected to the upper brush on the next ring. By cutting out 

* That is for 2000 and 1200 candle-power machines. On machines for 
4000 caudle-power, each pair of opposite coils is connected in multiple 
instead of as above described. 



HANDBOOK ON ENGINEERING. 



125 



the coils when they are in action, any loss due to dead resistance 
is prevented. 

The commutator segments are mounted on an insulated body, 
and when worn out may be easily replaced. 

Insulating break blocks for No. TJ and No. 8 machines are 
now made 2|" in length, but some old machines were i3rovided 
with 2|" blocks. With the 2|" blocks a higher voltage is 
obtained at the brushes, as the series combination of coils is 
maintained for a longer time before the coils are connected in 
multiple. The 2|" blocks may be used on machines formerly using 
2 1" blocks by cutting away a portion of the commutator segments. 

A new form of 
commutator^ shown 
in the accompanying 
illustration, has been 
designed for the No. 
1^ and No. 8 ma- 
chines and has im- 
proved segments. 
These segments may 
be turned end for end 
when one end becomes 
burned or worn, and 

each segment is interchangeable with the others. 
will not fit old commutator bodies. 




New seo'ments 



CONNECTIONS OF ALL BIPOLAR GENERATORS SMALLER 
THAN NO. 7^. 

The outside right-hand brush is connected to the large line 
binding post, while the inside right-hand brush is connected to 
the field and also to one of the small binding posts. The out- 
side left-hand brush is connected to the other small binding post 
and to the other side of the field circuit, while the inside left- 



126 



HANDBOOK ON ENGINEERING. 



hand brush is connected to the large binding post which connects 
to the other side of the line. 

CONNECTIONS OF NO. 7i AND NO. 8 BIPOLAR GENERATORS. 

The field switch on the later No. 7J and No. 8 machines is 
different from that of the smaller sizes, and there is but one 
small binding post for connection to the regulator. The internal 
connections of the regulator are also slightly different. The in- 



ClocU\A/ise 




Counter- ClocUvA/ise 



ci:: 







TT 



Amnnetet" 



'(UU 



Fig. 7. 



side terminal of one upper binding post K (see Fig. 7) is con- 
nected to the positive (left-hand) wire which connects the main 
binding post to the magnets M. The regulator connections for 
the earlier types of No. 7 J and No. 8 machines are the same as 
for smaller machines. 

As the No- 7^ and No. 8 machines have three commutator 
rings, cross-connections between the brushes are required as 
shown in the diagram. The outside left-hand brush is connected 
across to the middle right-hand brush, and the middle left-hand 
brush is connected to the inside right-hand brush. The inside 
left-hand brush is connected to the fields, and, on a new type 



HANDBOOK ON ENGINEERING. 127 

machine, to the shunt leading to the regulator. On the old type 
machines, the inside left-hand brush is connected to the right- 
hand small binding post. 

TO CHANGE DIRECTION OF ROTATION. 

A fi^ht-hand machine is one that revolves in a counter-clock- " 
wise direction when viewed from the commutator end, and a left- 
hand machine is one that revolves in a clockwise direction. Thus 
a right-hand machine will have the upper brushes on the right- 
hand side, and the lower ones on the left-hand side. 

To change a machine from right or counter clockwise, to left 
or clockwise rotation, simply reverse the connections given on 
pages 125 and 126 ; that is, read outside for inside smd vice versa. 
The diagram should be carefully studied and rigidly followed. 

In chang-ing- any of these types of machines for a different 
direction of rotation, the brush-holders should always be care- 
fully readjusted. 

The brush clamps must be changed to the opposite end of the 
rocker, and the beveled plates placed equally distant from the face 
of the commutator, and with their centers on an exact line across 
the center of the shaft. 

The rockers must all line up to bring the beveled plates on a 
level and equally distant from the commutator face. If neces- 
sary, paper may be used to adjust the level of these beveled 
plates. 

The commutator must be turned on the shaft, so that the seg- 
ment for any coil (bobbin) will lead it by the width of the coil. 
The screw fastening the commutator in position should be screwed 
into a hole drilled and tapped into the shaft, and, if the commu- 
tator is fitted with wood blocks, the blocks must be changed end 
for end. 

No- 7^ and No. 8 machines have no automatic rocking de- 
vice for the brushes. The amount of current is automaticallv 



12S 



HANDBOOK ON P^NGINEERING. 



controlled by a regulator which is attached to the wall or mounted 
on a suitable stand in the dynamo room. 



AUTOMATIC REGULATOR FOR BIPOLAR BRUSH ARC GENE- 
RATORS. 

The Brush Automatic Re§fulatoi* or " Dial " is shown in the 
accompanying illustration. It contains a variable resistance which 

is connected as a shunt to the 
fields, and automatically changed 
to increase or decrease the field 
current, and thus the voltage of 
the machine. The resistance is 
composed of columns of carbon 
plates which rest on the level L. 

"When the cufrent I'ises above 
normal, the magnets Jf draw up 
the level L and compress the car- 
bon columns, reducing their resist- 
ance and shunting more current 
from the fields. The electromo- 
tive force of the generator is thus 
reduced and the current maintained 
constant. As the resistance of the 
line is increased by the addition of 
lamps, the current in the magnets 
]\[ is diminished and the lever 
drops, separating the carbons and increasing the resistance of the 
shunt. More of the current must then pass through the genera- 
tor fields and raise the electromotive force of the machine. 

The dash pot P is to prevent sudden changes of resistance, 
and should be kept full of pure cylinder oil or glycerine. It 
should move easily, so that the regulator can respond quickly to 
chanoes in the current. 




HANDBOOK ON ENGINEERING. 129 

The variable resistance W, which is adjusted by the spring aS", 
is connected as a shunt to the magnet coils 3/ and regulates their 
current. The spring S should be kept as far to the left as prac- 
ticable, since a low shunt resistance increases the spark at the 
contact C and destroys it more rapidly, besides tending to make 
the regulator " pump," unless the dash pot is very stiff . The 
opening of the contact C is adjusted by the fiber nut N. With 
the shunt resistance properly adj usted and the lever in a midway 
position, the current can be increased by tightening the nut N, 
and decreased by loosening it. When the shunt resistance Wis 
once properly adjusted, it should not be changed, unless the 
magnets M are changed . 

To connect the regulator into the circuit, the main line is 
brought in at the large binding posts B, the positive being con- 
nected to the left-hand binding post. The current 77iust enter at 
the left hand. 

The small binding' post J is connected with the small binding 
post on the generator, so that the carbon resistance plates are in 
shunt with the field of the generator. 

While adjusting the regulator, the generator should run at 
normal speed, and the first test should be made on short circuit. 
If the current indicated by the ammeter is too low, the lever L 
should begin to drop at once and so increase the current. If this 
lever should stand at its lowest position and the current still re- 
main too low at full load, the speed of the generator must be 
increased. If the current is too high, the lever should rise and 
so reduce it; but if it fails to rise, the contact (7 should be 
examined. The current at this contact should spark all the time, 
but the contact should not open more than j-L". If it is not 
open when the current is too high, the fiber adjusting nut N 
should be loosened until the contact opens, when the lever will 
rise. If the lever rises when the contact is below normal, the 
nut N should be tightened. 

9 



130 HANDBOOK ON ENGINEERING. 

Center. Lines for No. 9 and No. 91-2 Generators. 




Center Lines for No. 10 Generator. 




f'FF 



Center Lines for No. 11 and No. 12 Generators. 



,-©- 



-^- 




nnu ^ 



A is Center Line of Bed-plate— Always Work from this Line. 

P and' C are Center Lines of Generators when Belted from Side 

Indicated by Arrow.T' 



HANDBOOK ON ENGINEERING. 131 

The resistance of the shunt TF should be so adjusted by re- 
moving the spring S that the lever will rise when the contact is 
opened and descend when the contact is closed. If it fails to 
descend, the resistance of the shunt should be decreased by mov- 
ing the sjjring JS to the right, which will shunt more current from 
the magnets Jf, and thus allow the lever to drop. When the 
generator is running at lightest load, the armature^! on the regu- 
lator should stand at its highest position — about i" from the 
magnets M. Should it touch the magnets, the set screw / should 
be turned to the right to draw the lever downward. 

Once in six months the carbon resistance columns should be 
loosened up and the dust and loose carbon particles blown out 
with a bellows. The regulator must then be readjusted. 

MULTIPOLAR BRUSH ARC GENERATORS. 

Each machine is provided with an iron bed-plate fitted with 
a ratchet and screw for sliding the machine to adjust the belt 
tension. This bed-plate should be securely fastened to a dry 
wood sub-base not less than 10" in thickness, except on wood 
floors, in which case 'it may be somewhat less, according to the 
thickness of the floor. 

Unless the gfenerator can be set up on a substantial floor, a 
foundation of masonry must be built. (See diagram No. 13396 
on page 134). 

The brick work is laid on a bedding of cement, and the sec- 
tion plates and bolts properly placed as the work progresses. 
The foundation bolts should be cut off at least 2" below the top 
of the wood sub-base and well covered with sulphur to insure 
complete insulation from the iron bed-plate. 

In whatever manner the bed-plate is mounted, the greatest 
care must be taken to have a thorough and permanent insulation 
rom earth. 



132 



HANDBOOK ON ENGINEERING. 



Four short bolts pass through the generator frame and are 
used to hold the niachine in position on its bed-plate. They are 
inserted in the slots in the iron base-plate, and provided with 
square nuts at their lower ends. The nuts must be placed in 
position before the bolts are inserted in the holes, and as the 
bolts are not long enough to reach the nuts if simply placed on 
the base under the bed-plate, the nuts must be raised at least 
1" by means of wood blocks. The bolts should be kept tight, 
except when adjusting the tension of the belt. 

To allow for stretching of the belt, the bed-plate should be so 
placed that the center line of the generator will be nearer the 
engine or counter-shaft than is the center line of the bed-plate. 
(See diagram on page 130.) The center lines are marked on 
the castings. 




Multipolar Brush Arc Generator. 



HANDBOOK ON ENGINEERING. 



133 




134 



HANDBOOK ON ENGINEERING. 



ASSEMBLY AND FOUNDATION FOR 
NOS. 9 AND 9g BRUSH ARC GENERATORS 



^1'?5ll1 




~^- 



1<-I5i"4- 151'-^ 
---- 4S' 



—\50- 

] I 

±1 



Brick ■Poundatipris sV-ioutd 
be pi-ovided vyitH cor>- 
cr-eta -TootinOs i-iot less 



be Oovei-ned bv CH© cHer- 
act^r- of the s6.l. BottdT- 



pendefTC of stetion f loon 



Diagram No. 13396. 



HANDBOOK ON ENGINEERING. 



135 



ASSEMBLY AND FOUNDATION FOR 
No. 10 BRUSH ARC GENERATOR 




Br-ick fou»->de>t'oi->s sHpuld 
be t>T-oN/ided wit»-> con- 
C7-eCe rootimrfs not less 
■t>-iar-v 6 iric>-<es deep- 
DeptK or roundAtior^ rrwjst 
be ooverned by t hie cHor-- 
occer- of the soil. Batter 
I to6. 
Fo^_Jrld^ltlor^ "Cimbers and 



Diagram No. 13397. 



136 



HANDBOOK ON ENGINEERING. 



ASSEMBLY AND FOUNDATION FOR 
Nos.l I AND 12 BRUSH ARC GENERATGRS 




H 54.° 





Noll 


Nol2 


n 


fl3|'. 


avr 


B. 


43',f 


^7ft 



_fpotirigs ■opt les: 



T It- of -the soil BoCeet- 

I to6. 

■" r>datiOT*i timbers. ar>d 



Diagram No. 13398. 



HANDBOOK ON ENGINEERING. 



137 



The various piirts ol' the niMchiue should ])e unpacked care- 
fully to prevent abrasion of the insulation and damage to the 
commutator. 
I The white lead should be carefully wiped off, especially from 

I the planed surfaces of the magnet yokes and the armature shaft. 




Method of fcJuspendiug Armature. 

The lower half of the frame is first placed in position on the 
bed-plate and bolted down. While this is being done, the ratchet 
screw for adjusting the belt should be screwed into the frame and 
slipped into place on the bed-plate as the frame is lowered. 

The lower halves of the bearing boxes should be removed 
and the oil chambers thoroughly cleaned and filled with a good 
quality of stringy oil, to the height indicated by the mark on the 
oil gauge. The lower halves of the bearing boxes may then be 
replaced. 



138 



HANDBOOK ON ENGINEERINCI. 



The proper method of suspending the ainiutiiie is shown on 
page 137. Before lowering it into place, the oil rings, which 
are always tied to the armature hub when shipped, should be 
put on the shaft. When placing the armature in its bearings, 
it is important to prevent the armature coils (bob])ins) from 
rubbing against the pole pieces. 



H^K:^ 


^^Bj^^^^P?^^^^^ ■' j^^^^ - ^ '■ ■- .>f^^mM fe^^^^^^^l 




■ 


^''^ 'f^i 




1 


^ _j 





Method of Handling the Magnet Yoke. 



The upper halves of the bearings with their cast-iron washers 
may next be j^ut on and securely bolted down with the clamping 
screws. 

When handling the magnet yokes, a rope sling should be 
used, as shown in the illustration above. The yoke should hang 



HANDBOOK ON ENGINEERING. 139 

very nearly level with the pole shoe slightly raised, so that in 
lowering the j^iece into place there will be no danger of chafing 
the armature coils or insolation. The bolts should be inserted as 
shown, and as the yoke is lowered, these will act as a guide and 
drop it into its proper place. The frame bolts must be screwed 
up especially tight, as any movement of the yokes while the 
machinery is running will ruin the armature. 

The brush-holder yoke and the regulator rocker arm should 
be put in place with a little oil on the bearing seats to insure 
freedom of movement through the entire range. 

The regulator is ready for operation when shipped, but a little 
light oil should be put into the gear housing, and the various 
bearings oiled through the oil holes, which are plugged with screws 
to exclude dust. It is also well to rub a little oil on the contact 
buttons of the rheostat. The small belt for the regulator should 
run open for either clockwise or counter clockwise machines. 

SETTING THE BRUSHES. 

A pressure brush should always be used over the under 
brush, as it improves the running of the commutator and 
secures a better contact on the segment. The combination is 
referred to as a " brush." The brushes should be set 5i" from 
tlie front side of the brass brush-holder. 

In setting the brushes, commence with the inner pair and set 
one brush about 5i" from the holder to the tip of brush, then 
rotate the rocker or armature until the tip of the brush is exactly 
in line with the end of a copper segment, as shown in Fig. 8. 
The other brush should be set on the corresponding segment 90° 
removed (the same relative position on the next forward segment) 
but if the length of the brush from the holder is less than 5i", 
move both brushes forward until the length of the shorter brush 
from the holder is 5i". Now set the two extreme outer brushes 



140 



HANDBOOK ON ENGINEERING. 



in the same manner, clamp- 
ing firmly in position, and 
by using a straight edge or 
steel rule, all the brushes 
can be set in exactly the 
same line and firmly se" 
cured. The spark on one 
of the six brushes may 
be a trifle longer than on 
the others. In this case, 
move the brush 




Fig. 9i 



Fig. 10.^ 



Fig. iii 



^ig' 8. 
forward a 

trifle so as to make the sparks on the six 
brushes about the same length. Equality in the 
spark lengths is not essential, but it gives at a 
glance an indication of the running condition of 
the machine. 

Brushes should not bear on the commutator 
less than i" from the point of the brush, or, as 
^ illustrated in Fig. 9, they will tend to drop into 
the commutator slots and pound the copper 
tip of the wood block. If, on the other hand, 
the bearing is too far from the end, or the 
brushes are set too long, as in Fig. 10, the point 
of the brush is lifted from the leaving end of 
the segment, causing sparking. 

Fig. \t shows correct setting with the tip of. 
the brush nearly tangential and still on the 
segment as it leaves. 



CARE OF COMMUTATOR. 

If the commutator needs lubrication, oil it very sparingly. 
Once or twice during a run is ample. If the oil has a tendency 



HANDBOOK ON ENGINEERING. 141 

to blacken the commutator instead of making it bright, wipe the 
commutator with a dry cloth. 

The machine, of course, generates high potential, and the 
cloth, or whatever is used to oil the commutator, should, there- 
fore, be placed on a stick so that the hand is not placed in any 
way between the brushes. 

A rubber mat should be provided for the attendant to stand 
on when working around the commutator and brushes. 

To prevent any possibility of shock, all switches on the termi- 
nal board should be closed. 

As soon as the current is shut off from the machine, the com- 
mutator should be cleaned. A piece of very fine sandpaper held 
against the corhmutator under a strip of wood for about a minute 
before the machine is stopped, will scour the commutator suffi- 
ciently. The brushes need not be removed. An effort should 
be made to have the machine cleaned immediately after it is shut 
down. Five minutes at that time will give better results than 
half an hour when the machine is cold. Never use a file, emery 
cloth, or crocus, on the commutator. New blocks will sometimes 
cause flashing, due to the presence of sap in the wood. The 
machine should be run for a few hours with a slightly longer 
spark, say i", and the commutator then thoroughly cleaned with 
fine sandpaper. 

CONNECTIONS OF MULTIPOLAR BRUSH ARC GENERATORS. 

Connections of Multipolar Brush Arc Generators are shown 
in Diagrams Nos. 13442, 13443, 13452. The current enters 
the field from the negative side of the circuit and takes the 
following course : Spool 1, to 2, to 7, to 8, to 5, to 6, to 3, 
to 4, to terminal board, to commutator. The field current is 
in the same direction for clockwise and counter clockwise 
machines. 



142 



HANDBOOK ON ENGINEERING. 



CO 



< 
CC 

u 



CHcc 
ID 

ceu 
OQtn 






i 

E 




_ffi 


Di 


.«^-" 


Srf. .1 


r 


i: 






•Q..*""' 




N^:^ 


i 




-. *• 




-•■?• -I— ] 


, 








r 


•VT. ••:.-- 


I ! 


.... ^..J 








2 -', 

CON 


I 







T^^ 



— <0 
C <B 

E-^ \ 

Q) (D 0) 

Fee: 





Diagram No. 1?)442, 



HANDBOOK ON ENGINEERING. 



14:3 




Diagram No. 13443. 



U4 



HANDBOOK ON ENGINEERING. 




Diagram No. 13452. 



HANDBOOK ON ENGINEERING. 



145 




Diagram No. 13453. 

10 



146 HANDBOOK ON ENGINEERING. 

TO CHANGE DIRECTION OF ROTATION. 

G>nncctions* — Remove the brush-holder cables and the studs 
from the rocker. Take off the brush-holder rocker, and revei?se 
it so as to bring the handle on the opposite side of the machine, 
changing, at the same time, the clamp stud to the same side as 
the handle. Replace the brush-holder studs in the rocker, but 
before setting, remove and reverse the brush-holders, so that the 
binding screws may be brought on the same side of the stud las 
the clips which hold the cables in position. Carefully square the 
brush-holders with the studs, and securely fasten, setting the 
studs according to instructions below. 

Remove the external rack at the lower end of the rocker arm , 
and replace by an internal rack, using the same insulation apd 
being careful to so align the rack that it will run freely through 
its entire arc. 

Settings brush-holder studs* — Remove the brush-holder caps 
and placing angle gauge A on the commutator as shown in Fig. 
12, turn the stud until the gauge rests 
squarely on the face of the brush- 
holder. Tighten the stud moderately, 
and repeat the operation on the extreme 
outer and inner rings of the commu- 
tator, noting the positions of brush- 
holder faces relative to the line at a in 
gauge (see Fig. 12). If the position of the line a relative to the 
face is not the same in both instances, the stud is not parallel to 
the commutator face and should be packed with mica or paper 
between the shoulder of the stud and the brush rocker till par- 
allelism is obtained; then tighten the studs securely in position. 
Care should be exercised in setting and securely fastening the 
stud in position, as noted above, as otherwise, the length, posi- 
tion, and tension of the brush will be changed. 




HANDBOOK ON ENOaNEERING. 147 

Connnatatots. — Remove the cuminutator segments aucl tarn 
the wood blocks end for end, or in such position that the brush 
in leaving the copper segment will come in contact with the 
copper tip of the wood block. It will also be found more con- 
venient to change the position of the switch handles on the termi- 
nal board, which can readily be done by removing the binding 
posts and switch posts and reversing their jDOsitions on the 
board. 

Connect up the brush-holders to the terminal board, as shown 
in the diagram of connections. 

Wires between controller and regulator should be reversed, and 
the clutch short circuiting cable (which is attached to the lower 
button on the left-hand side of the rheostat) should be carried to 
the opposite binding post with the wire from the left-hand lower 
binding post on the controller. 

The current of the Brush Arc Machine is automatically main- 
tained constant b}^ a regulator of one of the forms described on 
the following pages. 

FORM I REGULATOR FOR HULTIPOLAR BRUSH ARC QENE= 
RATORS. 

The Form i Regulator is placed on the frame of the machine 
beneath the commutator, and a constant motion is imparted to its 
main shaft through a small belt running around the armature 
shaft. (See Fig. 13.) By means of magnetic clutches and 
bevel gears, a pinion shaft is rotated, which moves the rack and 
the rocker arm and so shifts the brushes on the commutator to 
maintain a spark of about |" on short circuit and J" at full load ; 
at the same time the rheostat arm is moved over the contacts to 
cut resistances in or out of the shunt around the field circuit. 

The current for the magnetic clutches is regulated by the con- 
troller. 

The controller consists principally of two magnets which are 



148 



HANDBOOK OX ENGINEERING. 



energized by the main current and act when the current is too 

high or too low, by sending a small current to one of the clutches 

A careful examination of the controller (see Diagram 13454, 

page 150) in connection with Fig. 81 will give a clear idea of its 




To Controller 



regulating action. It is generally advantageous to make the yoke 
which carries the brushes on the machine and the arm moving the 
rheostat, rather tight. As the magnetic clutches act with con- 
siderable force, it -is not necessary to adjust these moving parts 



HANDBOOK ON ENGINEERING. 149 

SO loosely that they will move without considerable pressure on 
the rocker handle. Less difficulty will then be experienced in 
adjusting the controller. 

For shunt lamps the controller may be adjusted to permit a 
variation of .4 ampere above and below normal ; for differential 
lamps, the variation above and below should not exceed .2 ampere. 
The limits given in the following instructions are for differential 
lamps, and may be extended .2 ampere above and below for shunt 
lamps. 

if the controller is out of adjustment and fails to keep the cur- 
rent normal, do not try to adjust the tensions of both armatures 
at the same time. For example, suppose the current is too high, 
either one of the two spools may be out of adjustment. The 
left-hand spool J (see Diagram No. 13,454) may not take hold 
quickly enough, or the spool F may take hold too quickly. To 
make the adjustment, screw up the adjusting button /t on the 
right-hand spool, increasing the tension. This will have a ten- 
dency to let the current fall much lower before the armature 
comes in contact with H^ to cause the current to increase. By 
simply tapping the armature Q quickly with a pencil or piece of 
wood, forcing it down with its contact, and at the same time 
watching the ammeter, the current may be brought up to 6.8 am- 
peres if 6.6 amperes is normal, or 9.8 if 9.6 is normal. With 
the current at 6.8 amperes, which is .2 ampere high, the adjust- 
ing button L should be turned to increase the tension on this 
spring until the armature M comes in contact with contact N^ 
which will force current down through 0. The clutch which 
pulls the brushes forward and rocks the rheostat back for less 
current will thus be energized. Repeat this adjustment two or 
three times, but do not touch the adjusting button K; adjust L 
until it is just right. 

At the side of the armature M a little wedge is screwed in by 
means of an adjusting button, and increases or decreases the 



150 



HANDBOOK ON ENGINEERING. 




Diagram No. 13454. 



HANDBOOK ON ENGINEERING. 151 

leverage on this armature. See that this wedge is fairly well in 
between the core or frame of the spool and the spring of the 
armature. The armature M may have to be taken out and the 
spring slightly bent. It is advisable to have the screw which 
passes through the adjuster button L about half way in, to allow 
an equal distance up and down for adjusting this lighter spring 
after the wedge-shaped piece is in the right position to give the 
necessary tension on the spring which is fastened to the arma- 
ture M. 

In the right-hand corner P, a small bent piece of wire is 
placed for tightening up the screw which fastens the spring to 
the frame of the spool. As the contact made by the spring and 
the frame of the spool held together by a screw and button is a 
part of the magnetic circuit, it will be almost impossible to get 
this spring back to exactly the same tension after once moving it. 
Therefore, the adjusting buttons of the controller must be turned 
slightly in order to bring it back to its proper adjustment. This, 
however, is an after consideration, and care should be taken to 
have the screw which holds the spring and frame together always 
tight. 

Having adjusted the spool 1 so that the current will not rise 
above 6.8 (or 9.8) amperes, move the armature M up to contact 
N with a pencil or piece of wood, causing the current to be re- 
duced to about 6.2 (or 9.2). After the current settles at this 
point, decrease the tension on the spring which is fastened to 
armature 6r, allowing ' this armature to fall down to contact H, 
Current will then flow through Q, which will rock the brushes 
back and also move the rheostat arm for more current. As the 
spool /has been adjusted for 6.8 (or 9.8) amperes, the current 
cannot rise above that amount, no matter how the spool F is 
adjusted. 

With a very little practice in moving the armature of one 
spool with a pencil, the other can be adjusted much more readily 



152 HANDBOOK ON ENGINEERING. 

than if an attempt is made to adjust the screws ii" and L at the 
same time. 

The two small shunt coils, R and S^ are connected around the 
two contacts simply to decrease the spark between the silver and 
platinum contacts. If they should become short circuited in any 
way, so that their resistance becomes diminished, sufficient cur- 
rent may pass through either of them to operate the regulator. 
If unable to locate the trouble, disconnect these coils at points T 
and ?7, when a thorough examination can be readily made. M 
and G need not move more than just enough to open the con- 
tact — -J-2" is ample. 

STARTING THE MULTIPOLAR BRUSH ARC GENERATOR 
WITH FORM I REGULATOR. 

In starting", the lower switch, which short circuits the field, 
should be opened last. 

The switch in the left-hand corner of the controller (Diagram 
No. 13454) cuts out the two resistance wires which are used to 
force the current through wires and Q to the clutches. Open 
this switch which leaves the automatic device of the controller in 
circuit so that it will move the brush rocker. Unclasp the brush 
rocker from the rheostat rocker. Move the brushes by hand to 
give the proper spark, allowing the rheostat arm, however, to be 
moved by the controller. After the switches are opened, the 
rheostat arm will go clear around to a full load position, and 
then, as the current rises, the controller takes hold and brings the 
arm back. In the meantime, rock the brushes forward or 
backward and keep the spark about the proper length, say i" at 
full load to I" on short circuit. Gradually the rheostat arm will 
settle, the spark will become constant, and the machine will give 
its proper current. Then clamp the rocker and rheostat arm 
together and let the machine regulate itself. 

This method is much better than opening the switches on the 



HANDBOOK ON ENGINEERING. 



153 



uiacliiiie and allowing the wall controller to take care of the 
machine from the start. By allowing the controller to start the 
machine, a trifle longer spark is obtained than by the other method, 
unless the machine is run from the beginning on a very full load. 
The machine will require a trifle longer spark on light loads, 
or on bad circuits, than when running at full load. This fact 
should be borne in mind in wet weather, when trouble with 
grounds is experienced. 




Form 2 Regulator. 



FORM 2 REGULATOR FOR MULTIPOLAR BUSH ARC 
GENERATORS. 

The connections for clockwise and counter clockwise genera- 
tors of the single circuit or multi-circuit type, are shown in Dia- 



154 HANDBOOK ON ENGINEERING. 

grams Nos. 13452 and 13453 on pages 144 and 145. The con- 
nections of the field magnets are the same for either clockwise 
or counter clockwise. 

The switches on the terminal board should be arranged as 
shown in Diagram No. 13452 for clockwise, and No. 13453 for 
counter clockwise single circuit generators. The counter clock- 
wise generator has a straight vertical strap connecting the two 
vertical clip posts. The clockwise generator has a diagonal 
strap. The terminals of the machine are on the back of the 
board. 

A, the positive tefminal, is connected through the board to 
the switch post ; 5, the negative terminal, is insulated from the 
switch clip post, and is used only as a connector for the cable 
running down to B^ on the regulator. In returning to the 
machine, the current can go directly to B^ instead of to B. 

The connections of the Form 2 Regulator are shown in Fig. 
14. The regulator performs two operations ; sweeps a set of 
contacts, throwing more or less resistance in shunt with the 
field circuit, and at the same time, rocks the' brushes so that the 
spark is kept at proper length, varying at from J" at fuU load to 
I" on short circuit. 

A small belt runs over the armature shaft M and drives the 
rotary oil pump P. The pump draws the oil from the containing 
case and forces it through passages to the valve T, a section 
of which is shown in Fig. 15. 

The ports overlap this valve so that the oil may flow through 
when the valve is in its central position. The valve is con- 
trolled by the electromagnet F (Fig 14) which actuates the 
armature U and the lever H. The pull on armature U varies 
with the strength of the current which excites F. The opposite 
end of the lever H is attached to spring G, which is adjusted by 
the screw nut E so as to hold the valve in central position when 
normal current is flowing through the controlling magnet. 



HANDBOOK ON ENGINEEEING. 



155 




Fig. 14. 



156 



HANDBOOK ON ENGINEERING. 



If the current is too strong, it pulls down the armature t/, 
raising the valve, throwing more oil on the upper side of the 
circular piston head S, and allowing the oil to run out from the 




lower side, thus forcing the piston X around clockwise, lowering 
the current by moving the contact arm so as to shunt more cur- 
rent from the fields, at the same time moving the brushes for- 
ward until the current returns to its normal value. 
If the current is too low the operation is reversed. 



ADJUSTMENT OF FORM 2 REGULATOR. 

To raise the current, turn the hard rubber nut E (Fig. 14) to 
the right. If the current is too liigh, turn the nut to the left. 

The limits between which the regulator operates are deter- 
mined by the number of turns in the spring G. If the spring G 



HANDBOOK ON ENGINEERING. 



157 



is stiffened by cutting off some of the turns and stretching it out, 
the limits of regulation will be wider. If the spring has a greater 
number of turns, it will regulate within narrower limits, but be 
more liable to "pump." The regulators are shipped with 
springs which have been found to give the best service for usual 
conditions. 

The regulator may be caused to operate quickly in one direc- 
tion and slowly in the reverse direction by changing the position 
of the stops on lever H. By raising the stop on the right-hand 
side of lever H^ the movement on increasing the current will be 
retarded . 

The safety of relief valve, shown in Fig. 16, is set to operate 
at a pressure of about fifteen pounds to the square inch, so as to 




The arrows show 
the path of the oil 
througli the pump 
for counter clock- 
wise rotation, and 
the stopping plugs 
are located for a 
machine running in 
this direction. 



Fip-. 10. 



relieve the pump. Fig. 1(3 also shows the ports and the method 
of changing the plugs, so as to run the pump with an open belt 
for either clockwise or counter clockwise machines. There is a 



158 HANDBOOK ON ENGINEERING. 

small wire on the back of the circular piston, which may be 
screwed into the plugs in these passages for the purpose of draw- 
ing them out and changing their position. 

STARTING THE MULTIPOLAR BRUSH ARC GENERATOR WITH 
FORM 2 REGULATOR. 

Before starting the machine, the oil box of the regulator should 
be filled with a light spindle or dynamo oil nearly up to the shaft 
which carries the contact arm, etc. As soon as the machine is 
started, the level of the oil will be somewhat lowered. 

If the pump fails to start promptly, it may be started by shift- 
ing the brushes backward and forward, and moving the contact 
arm, to force out the air and draw in the oil. 

In a newly installed machine, the oil should be changed at 
least once a week for the first month or six weeks, until all dirt 
and grit are thoroughly removed. The oil may be drawn off by 
unscrewing the cap bolt at the bottom of the oil box. 

Special care has been taken to provide a good fitting cover for 
the oil box, so as to prevent sand and dirt from getting into the 
oil when the commutator is cleaned. The cover must always be 
kept on. 

In general. Brush machines with Form 2 Regulators are started 
as described on page 152, but the following additional instructions 
should be noted : — 

Having correctly adjusted the regulator for the desired cur- 
rent, as previously described, the starting valve handle S^ (Figs. 
14 and 15) should be turned counter clockwise when the machine 
is running without load. This handle operates a valve which 
connects both sides of the circular cylinder, thereby giving a free 
flow of oil between the two sides, and preventing the operation of 
the piston and relieving the pump from any undue load. 

To put the machine in operation, the valve should be gradu- 



HANDBOOK ON ENGINEERING. 159 

ally thrown around clockwise, cutting off the flow of oil from the 
two sides of the cylinder after the switches have been opened. 
This valve may also be used to throw the regulator out of opera- 
tion if desired. 

FORM 3 REGULATOR FOR MULTIPOLAR BRUSH ARC QENE= 
RATORS. 

In the Form 3 Regulator a belt from the armature shaft runs 
a small countershaft with crank attached. A rocking or recipro- 
cating motion is thus imparted to the main lever, on which are 
pivoted two self-adjusting clutch jaws or grips. When the cur- 
rent is normal, the clutches are held stationary, but as the current 
varies, either above or below normal, the clutch on one side is 
dropped so that it will grip the clutch disk, and the mechanism 
revolves in the proper direction to restore the current. 

With slight variations of the current, the regulator contact 
arm is moved forward or backward very slowly; while, with 
greater variations, caused by any considerable number of lamps 
being cut in or out, the movement is increased and the normal 
point or position more quickly reached. 

The same form of bell magnet is used as in the Form 2 Regu- 
lator, and it is adjusted in the same manner (see pages 156 and 
157). 

For starting Brush Arc Generators with Form 3 Regulators, 
see general directions under Form 1 Regulator on page 152. 

FORfl 4 REGULATOR FOR flULTIPOLAR BRUSH ARC QEN= 
ERATORS. 

The Form 4 Regulator is similar to the Form 3 ; the counter- 
shaft and rocking lever are identical, but instead of using clutches, 
the lever operates two pawls, which engage in ratchet wheels. 
The pawls are not in contact when the current is normal, but are 



160 HANDBOOK ON ENGINEERING. 

thrown iu to move the arm to either right or left as the current 
varies and the regulator is called upon to shunt more or less 
current from the field. 

With this form of regulator, the motion is positive, and the 
ratchets are advanced by the full length of one tooth, whether the 
variation in current be great or small. The ratchets are so 
arranged that the contact arm moves across no more than one and 
one-half of the contact buttons for each tooth. 

AnnETER. 

A reliable ammeter should always be connected in the circuit 
of an arc generator, so that the exact current may be read at a 
glance. It should be connected into the negative side of the line 
where the circuit leaves the regulator. 

INSTRUCTIONS FOR INSTALLING AND OPERATING mPROVED 
BRUSH ARC LAMPS. 

Unpacking. — Remove all strings and wedges from the mech- 
anism, and carefully clean the lamp^ using a small bellows to 
remove dust and any pieces of packing which may have lodged 
inside the casing. 

Examine the packing carefully for small pieces of the lamp 
which may be wrapped up separately, or possibly have worked 
loose during transportation. 

Suspension. — One of three methods of suspension may be 
used for Brush Arc Lamps. If chimney suspension, which is the 
most common, is adopted, the wire, cable or rope used to suspend 
the lamp must be carefully insulated from the chimney. For this 
purpose a porcelain insulator should be inserted between the 
support and the lamp. 

Hook suspensions niay l^e used to advantage in some places, 
but greater care must be taken to insulate the supporting wires 



HANDBOOK ON ENGINEERING. 



161 





-. 1 


-n n n 


p. 




CD CD ^ I r h — -^^ — 

nnin"' n ^ ■ 1 ■ 


~ r 


- — 


8 

T 


if 314 


1 


—J p 

1^1 




► 







z 
o 

Ui 

CO 

5§ 

— z 

CI m 
33° 

"n 
en a 
mz 
zz 

SB 
^~ 




03 



Diagram No. 13444. 



162 



HANDBOOK ON ENGINEERING. 




Diagram No.- 13445, 



HANDBOOK ON ENGINEERING. 1H3 

from any conductors, as the hooks form the terminals of the 
lamp. 

The most convenient arrangement for indoor use is to suspend 
the lamp from a hanger board. The porcelain base of the hanger 
board prevents short circuits or grounds. 

A protecting hood is not necessary for outdoor use, as the 
lamp chimney and its base are one casting and effectually exclude 
rain or snow water. 

If the magnets have become damaged, new ones should be 
substituted, and the lamp readjusted. 

The lamps run nominally on circuits of 6.6 amperes for 1200 
candle-power and 9.6 amperes for 2000 candle-power. In case 
it is necessary to run a lamp on a circuit differing from the 
standard, the lamp may be adjusted by moving the contact on 
the adjuster. This will compensate for about one ampere either 
way from normal and is set in about the middle position when 
the lamp is shipped. 

Permanent adjustment for special circuits of variation greater 
than one ampere from standard is made by filing the soft iron 
armature. The clutch should be so adjusted that the center of 
the armature is i|" above the plate when the trip on the first rod 
is touching the bushing, and ii " when the trip on the second rod 
is in a similar position. A small gauge is convenient for adjust- 
ing the clutch. The position of the trip of the clutch determines 
the feeding point of the lamp. 

After thoroughly repairing and cleaning the lamp, it should 
be run a short time before installing. Lamps should not be 
tested in an exposed place, as a strong draft of air will cause 
unpleasant hissing, which may be mistaken for some internal 
trouble. 

Lamps should "ot hiss or flame if good carbons are used. A 
voltmeter should always be used when adjusting or testing. 

Connecting* — The lamp terminal hooks are marked P (posi- 



164 HANDBOOK ON ENGINEERING. 

tive) and N (negative), and should be connected into circuit 
accordingly. 

In the Form i lamp, both upper and lower carbon holders 
are adjustable for various sizes of carbons, but, when shipped, the 
holders are adjusted for Jg" carbons. The upper carbon holder 
of the Form 2 lamp is made in two sizes, one taking Jg" to i'' 
carbons and the other taking -f^" to |". The lower carbon-holder 
is adjustible as in the Form 1 lamp. If the carbons are straight, 
they should line up properly. The carbons must be clamped 
firmly to prevent heating or possibility of arcing at the holder. 

The carbons should rest in contact when the lamp is cut out. 
When the switch is opened, part of the current from the positive 
terminal hook (P) goes through the adjuster to the yoke, and 
thence through the carbon rod and carbons to the negative ter- 
minal hook (^N), The remainder of the current goes to the cut- 
out block, but, as the cut-out is closed at first, the current crosses 
over through the cut-out bar to the starting resistance, and so to 
the negative side of the lamp. A part of it, however, is shunted 
at the cut-out block through the coarse wire of the magnets, and 
so to the upper carbon rod and carbons and out. This shunted 
current energizes the magnets and so raises the armature which 
opens the cut-out and at the same time establishes the arc by 
separating the carbons. 

The fine wire winding is connected in the opposite direction 
from the coarse winding, and its attraction is therefore opposite. 
When the arc increases in length, its resistance increases, and 
consequently, the current in the fine wire is increased. The 
attraction of the coarse wire winding is, therefore, partly overcome 
and the armature begins to fall. As it falls, the arc is shortened 
and the current in the fine wire decreases. The mechanism feeds 
the carbons and regulates the arc so gradually that a perfectly 
steady arc is maintained. 

The fine wire of the magnets is connected in series with the 



HANDBOOK ON ENGINEERING. 



165 



winding of ii small uuxilitiry cnl-out niagnel at the l,o[) uf the 
mechanism. 




CONNECTIONS FOR IMPROVED BRUSH ARC LAMPS. 

This magnet^ which also has a supplementary coarse winding, 
does not raise its armature unless the voltage at the arc increases 



166 HANDBOOK ON ENGINEERING. 

to 70 volts. The two Avindings counect at the inside terminal 
on the lower side of the auxiliary cut-out magnet, and the current 
from the fine wire of the main magnets passes through both wind- 
ings and then to the cut-out block and so to the starting resist- 
ance and out. 

If the main current through the carbon is interrupted (as by 
breaking of the carbons), the whole current of the lamp passes 
through the fine wire circuit. Before this excessive current has 
time to overheat the fine wire circuit, it energizes the auxiliary 
cut-out magnet and closes a circuit directly across the lamp 
through the coarse wire on the auxiliary cut-out to the main cut- 
out block, and thence to the negative terminal. 

The auxiliary cut-out operates instantly and prevents any 
danger to the magnets during the short period required for the 
main armature to drop and throw in the main cut-out. When the 
main cut-out operates, the armature of the auxiliary cut-out fails, 
because there is not sufficient current in that circuit to energize 
the magnet. 

The voltag'e at which the auxiliary cut-out magnet operates 
depends on the position of its armature, which is regulated by 
the screw securing the armature in position. It should not be 
adjusted to operate at less than 70 volts. 

Trimming"* — The globe may be lowered by releasing a thumb 
screw at the side of the holder. When lowered, the globe is sup- 
ported by a center rod with a crown which engages the lower 
carbon-holder stand. 

The carbons should be solid and of uniform quality. For the 
best results, the upper carbon should be 12" x J-^'\ and the 
lower 7" x 7 J^". The stub of the upper carbon may then be 
used in the lower holder when retrimming. 

At each trimming the rod should be carefully wiped with 
clean cotton waste. It should never be pushed up into the lamp 
in a dirty condition. 



HANDBOOK ON ENGINEERING. 



167 



In order to remove the carbon rod or examine the mechanism 
the jacket must be lowered by pressing a spring clip on its under 
side. 

The carbon rod may be unscrewed and removed by a small 
screw-driver or small strip of metal inserted in the slot cut in the 
rod cap. The cap will remain in the hole through the yoke when 
the rod is taken out. 

The lamp must never be left burning with the jacket off, nor 
be allowed to hang with the mechanism exposed to the weather. 

Repairing, cleaning: and testings — If the lamps show a ten- 
dency to hiss or work badly after long service, they should be 
removed to a convenient place and carefully inspected. 

AH wearing parts should be examined, and, if necessary, 
renewed by ordering new parts. 



TABLE SHOWING RELATIVE llESISTANCE OF METALS AT TEMPERA- 
TURE OF 70 DEGREES F. 



NAME OP METAL. 


Resistance in Ohms of Wire 100 ft. long and 
one-thousandths of an inch in diameter. 




965 

1,030 

1,328 

1,900 

3,600 

5,700 

6,400 

7,500 

8,500 

12,600 

12,700 

23,000 

42,000 

57,700 

3,792,000 


Remarks. 


Silver 




CoDDer 


The resistance of arc light car- 


Gold 


bons is given for comparison and, 


Aluminum 


as will be noticed, it is about 


Zinc 


4 000 times as great as that of 


Platinum 


silver. 


Iron, Wrought 

Nickel 


To obtain the resistance of 


Tin 


100 ft. of wire of any size, divide 


German Silver 

Lead 


the figures in this table by the 
square of the diameter of the 


Antimony , 


wire in thousandths of an inch. 


Manganese Steel.... 
TVrpvonrv 




Arc Light Carbon.. 





HANDBOOK ON ENGINEERING. 




Fig. 1 . The Thomson-Houston Standard Arc Dynamo 
Arranged for Right-hand Rotation. 



CHAPTER X. 

INSTALLATION OF ARC DYNAMOS. 

Location and mounting, — The generator should be located 
in a cool, dry room, free from dust, metal chips or flying parti- 
cles of any sort. Space should be allowed around the machine to 
give ample room for reaching all parts of it, particularly the 
commutator. The generator must not be placed in a room where 



HANDBOOK ON ENGINEERING. 169 

moisture is liable to collect upon it. Basements are often very 
objectionable on this account. The generator should be set upon 
a firm foundation of well-seasoned wood, and should be mounted 
upon a sliding bed -plate, so that the belt can be tightened or 
loosened while the generator is running. The generator should 
be thoroughly insulated from earth. The sliding bed-plates as 
now manufactured are designed to provide perfect insulation, and 
meet this requirement fully. The direction of rotation of the 
armature in the standard generator is from right to left, or 
counter-clockwise, as seen when facing the commutator. This is 
called a right-hand machine. Right-hand machines may be run 
left-handed by replacing certain parts of the brush-holder and 
regulating mechanism, per instructions on page 185. 

Pulleys* — The generator is provided with a pulley of proper 
size to transmit the power demanded, and a smaller one should 
not be substituted. 

Bearings* — The oil in the reservoir should be renewed once a 
week for the first two or three weeks, in order to wash out any 
grit which might become loosened by the churning of the oil while 
the machine is running. 

Speed* — The generator should be run as nearly as possible at 
the speed given by the maker. An increase of speed, if not too 
excessive, will do no harm, but a considerable diminution in 
speed below normal, when the generator is doing its maximum 
work, is liable to cause unsteadiness in the lights. 

The automatic regulator will adjust perfectly for fluctuations 
in speed near or above normal, unless the fluctuations are 
extremely sudden, as in the case of slipping of the belt. 

Belts* — The belt of the generator should be about half an 
inch narrower than the face of the pulley. An endless belt is 
desirable. 

Brushes* — When the generator is in position the brushes or 
strips of copper B B, B^ B^ (see Fig. 2), are placed on the 



170 



HANDBOOK ON ENGINEERING. 




I)©© 



=Qc= 




CONNECTIONS FOR ARC LIQHTINQ SYSTEM. 

Fig. 2. 



HANDBOOK ON ENGINEERING. 171 

machine in tlie manner shown. All four brushes should be set 
exactly to the gauges sent with each machine, so that they press 
with sufficient force on the surface of the commutator to insure 
good contact at all times. 

The leng'th of the ^auge is such that the brushes project a 
little past the center of the commutator, as shown in Fig. 5, 
to avoid catching in the slots should the armature be turned 
backward. 

Air Blast* — The air blast or blower on the arc light genera- 
tor plays an important part in the successful operation of the 
machine. Its construction is very simple ; it has but few moving 
parts and these are made strong and durable. The air blast re- 
quires no attention, excej^t that it should be kept scrupulously 
clean and well oiled. Only the best quality of mineral oil should 
be used. Poor oil will always cause trouble. 

The screens which cover the air inlets on the air blast, should be 
kept clean and free from dust. They should be taken out about 
once a month and cleaned in kerosene oil. If it should become 
necessary to cut a new air blast keyway the proper place to cut 
it is exactly one-third of the way round from the old one. 

Regfulator* — The regulator is fastened to the frame of the 
machine by two short bolts. On the right-hand machine its posi- 
tion is on the left-hand side, as shown in Fig. 2. On the left- 
hand machine, i. e., one which runs clockwise, its position is on the 
opposite side. Before filling the dash-pot D with glycerine, see 
that the regulator lever and its connections, brush yokes, etc., 
are free in every joint, and that the lever L can move freely up 
and down. Then fill the dash-pot Z> with concentrated glycerine. 
The long wire from the regulator magnet M. is connected with 
the left-hand binding post P of the machine, and the short wire 
with the post P- on the side of the machine. The inside wire of 
the field magnet, or that leaving the iron flange of the left-hand 
field should be connected into the post P^ also, as shown in Fig. 



172 



HANDBOOK ON ENGINEERING. 



2. The electric current (see Fig. o), should be complete from 
P^ on the controller magnet, through the lamps to post ^ on the 
machine, through the right-hand field magnet O^, to the brushes 




CONNECTIONS FOR RHEOSTAT, 

Fiff. 3. 



B^ jBI, through the commutator and armature to the brushes 
B B, through the left-hand field 0, to posts F^ and P, thence to 
posts P2 and P on the controller magnet, through the controller 
magnet to P^ The current passes in the direction indicated by 
the arrows. 

Rheostat* — When an arc machine is to be run frequently at a 
small fraction of its normal capacity, the use of a light load 
device is advisable to secure the best results in regulation. 

The rheostat (see Fig. 5) is connected in shunt with the right 
field of the generator. Facing the rheostat with right binding 
posts at the bottom, the contact on right side or No. 1 gives open 
circuit and throws the rheostat out of use. Point No. 2 gives a 
resistance of 44 to 46 ohms, and point No. 3 gives a resistance of 
20 to 22 ohms. 



HANDBOOK ON ENGINEERING. 



173 



This rheostat is regularly shipped with MB^-, 75 light gene- 
rators and allows the following variations : Point 1, 75 to 48 
lights; Point 2, 48 to 25 lights; Point 3, 25 lights or less. 
For use with other sizes of generators, the adjustment of the 
rheostat must be made to suit the conditions. 

When the rheostat is in use, the sparks at the commutator 
will be somewhat larger than normal, but will not be detri- 
mental. 

p. 




CONTROLLER FOR ARC DYNAMO. 

Fig. 4. 

ContfoUen — The controller magnet (see Fig. 4) is to be fast- 
ened securely by screws to the wall or some rigid upright sup- 



174 HANDBOOK ON ENGINEERING. 

port, taking care to have it perfectly plumb. It is connected to 
the machine in the manner shown in Fig. 3, i. e., the binding post 
P2 on the controller magnet, is connected to the binding post F^ 
(see Fig. 2) on the end of the machine; and likewise, the post 
P on the controller to the post P on the leg of the machine ; the 
post P^ forms the positive terminal from which the circuit is to 
run to the lamps and back to N. 

Great care should be taken to see that wires P P and P^ P^ 
are fastened securely in place ; for if the connection between P 
and P should be impaired or broken, the regular magnet JW would 
be thrown out of action, thus throwing on the full power of the 
machine, and if the wires P^ P^ should become loosened, the full 
power of the magnet i)f would be thrown on, and the regulator 
lever X, rising in consequence, would greatly weaken or put out 
the lights. 

The wires leading from the controller magnet to the machine 
should have an extra heavy insulation. Care should be taken in 
putting up the controller magnet that the following directions are 
followed : — 

(1) The cores B of the axial magnets C C must hang ex- 
actly in the center, and be free to move up and down. 

(2) The screws fastening the yoke or tie pieces to the two 
cores must not become loosened. 

(3) The contacts must be firmly closed when the cores are 
not attracted by the coils C C, which is the case, of course, 
when no current is being generated by the machine, and when the 
cores are lifted, the contacts must open from ■^^" to J^" 5 ^ 
greater opening than ^l" ^las the effect of lengthening the time 
of action of the regulator magnet. This tends to render the cur- 
rent unsteady, and in case of a very weak dashpot or short cir- 
cuit, might cause flashing. Adjustment may be made if necessary 
by bending the lower contact up or down, taking care that it. is 
kept parallel with the upper contact, so that when they are closed. 



HANDBOOK ON ENGINEERING. 175 

contact will be made across its whole width. If this adjustment 
is not properly made there will be destructive sparking on a 
small portion of the contact surfaces. 

(4) All connections must be perfectly secure. 

(5) The check-nuts JSf must be tight. 

(6) The carbons in the tubes L must be whole. 

These carbons form a permanent shunt of high resistance 
around the regulator magnet 3f, and if broken will cause de- 
structive sparking at contacts 0, burning them and seriously 
interfering with close regulation of the generator. In case a 
carbon should become broken, temporary rej^airs may be made 
by splicing the broken piece with fine copper wire. To keep the 
action of the controller perfect, the contacts should be occa- 
sionally cleaned by inserting a folded i^iece of fine emery cloth 
and drawing it back and forth. 

The amount of currrent generated by each machine dei3ends 
upon the adjustment of the si3ring jS. If the tension of this 
spring is increased, the current will be diminished ; if the tension 
is diminished, the current will be increased. 

Once set up and in perfect working condition, adjusted to the 
proper current, the controller magnet should rarely need any 
adjustment. 

Testing: arc Ii§fht dynamos. — The points here noted are very 
essential to the successful operation of the arc generator, and are 
very carefully carried out in testing arc machines at the factory. 
They are given for the benefit of those who have not had experi- 
ence in that line. The commutator should fit the shaft snugly, 
but be sufficiently free to turn easily on the shaft. Be very careful 
to put the short brush-holders on the outer yoke, and the long 
brush-holders on the inner yoke. Also see that the long binding- 
post, attached to the sliding connection, is on the lower left-hand 
brush-holder, and the short post on the lower right-hand brush- 
holder, Always set the brush-holders to the proper angle by the 



176 



HANDBOOK ON ENGINEERING. 




ifi 




A — Commutator Segments. 
g4 I Primary Brushes, 
gs [ Secondary Brushes. 



C— Forward Point of Segnient. 
D— Point of Brusii. 
E— Brush-holders. 
F— Point of Contact. 



Figs. 5 and 6. 



HANDBOOK ON ENGINEERING. 177 

brush-holder gauge. First tighten up the brush-holders and then 
turn them to the correct position b^^ means of a piece of steel wire 
passed through the holes. Then permanently tighten up the 
brush-holders very firmly, trying them with the gauge to see that 
they are the same distance from the commutator. Always be 
careful to get the brushes exactly straight and flat before clamp- 
ing them to the brush-holders, and always set them to the exact 
length of the brush gauge. 

Setting the cut-out. — After the brushes are in position, the 
cut-out must be set. This is done by turning the commutator on 
the shaft in the direction of rotation (if the commutator is set in 
position the whole armature must be revolved), until any two 
segments are just touching the primary brush on that side, as 
segments xV and A" ' touch brush B^ in Fig. 6. Under these 
conditions brush B^ should be at the left-hand edge of upper 
segment. Then turn commutator until the same two segments are 
just touching brush 5^, when the end of brush B^ should just 
come to the right-hand edge of the lower segment. If the second- 
ary brush projects beyond the edge of the segment the regulator 
arm should be bent down ; if it does not come to the edge of the 
segment the arm should be bent up. 

Care must be taken that the regulator armature is down on the 
stop when the cut-out is being set. These adjustments by bend- 
ing regulator arm are always made in the factory before testing the 
machine, and should never be made on machines away from the 
factory unless the regulator arm has been bent by accident. If it 
becomes necessary to make any adjustments they should be 
made by means of the sliding connection attached to the inner 
yoke. 

Always try the cut-out on both primary brushes. If it does 
not come the same on both, turn one oyer. If the brush-holders 
are correctly set by the gauge, there should be no trouble in get- 
ting the cut-out set properly after one or two trials. 

12 



178 



HANDBOOK ON ENGINEERING. 




KIQHT^AND RING ARMATURE. 




RiaHT-HAND DRUM ARMATURE. 

Figs. 7 and 8. 



HANDBOOK ON ENGINEERING. 179 

To set the commutator iu the proper position on a right-hand 
machine, with a ring armature, find the leading wire of No. 1 
coil. It is the custom in the factory to paint this lead red, also 
to paint a red mark on the center band between the two groups of 
coils, namely, the last half of No. 1 coil and the first half of No. 
3 coil. The first half of a coil is that group from which the lead 
comes. The last half is diametrically opposite the first half, and 
the lead wire belonging to it is connected with the brass ring on 
the outside of the connection disk on the commutator end. 

In Fig* 7 the first halves of the three coils are represented by 
1,2, and 3, and the last halves by 1', 2', and 3'. A narrow piece 
of tin with sharply pointed ends is bent up over the sides of the 
middle band at the center of the red mark, so that the points are 
opposite each other. When the red mark and red lead have been 
found, turn the armature until the last half of No. 1 coil has 
wholly disappeared under the left field, and until the left-hand edge 
of the first coil to the right of the red mark (No. 3 in Fig. 7) is just 
in line with the edge of the left field. The red lead will then be in 
position shown in Fig. 7, and the armature is in proper position to 
set the commutator. In the case of the right-hand drum armature, 
the leading wire of the first coil should be found. This lead may 
be recognized from the fact that it is more heavily insulated than 
the rest, and is found in the center of the outer coil, on the commu- 
tator end. With this wire turned underneath, rotate the armature 
forward, or counter-clockwise, until the pegs on the right-hand 
side of this coil just disappear under the left field (see Fig. 8). 

The position of the red lead and the red mark on the band are 
the same on all armatures, but their positions in the fields of 
machines called left-hand (clockwise rotation) should be as shown 
in Figs. 9 and 10, when setting the commutator. 

When the armature of a right-hand machine is in position, the 
commutator is turned on the sliaft until segment No. 1 is in the 
same relative position as the last half of No. 1 coil ; segment No, 



180 



HANDBOOK ON ENGINEERING. 




LEFT=HAND DRUM ARMATURE. 

Fio-. 9. 




LEFT-HAND RING ARMATURE. 

Fio-. 10. 



HANDBOOK ON ENGINEEETNG. 181 

2 should correspond Avith last half of No. 2 coil, aud segment No. 

3 with last half of No. 3 coil, as shown on Figs. 7 and 8. 
For left-hand machines, see Figs. 9 and 10. 

The distance from the tip of the brnsh, which is on top, to the 
left-hand edge of No. 2 segment on a right-hand machine, or to 
the right-hand edge of No. 3 segment in a left-hand machine, is 
called the lead, and should be made to correspond to the following 
table : — 

TABLE OF LEADS 



DRUM ARMATURES. 


RING ARMATURES. 


C^'-^ 1" positive. 


lO- ^\" positive. 


C. 1" u 


K2 ^" u 


&^^Y " 


M^^ 1" negative. 


E^r " 


M2 1" 


H12 1" " 


LD12 1" positive. 


H2 1" u 


LD2 1" .^ 




MD12 13" - 



MD2 If" " 

Place the screws in the binding posts at the lower ends of the 
sliding connections and put on the dash-pot connections between 
the brushes, with the heads of the connecting screws outward. 
In every case the barrel part of the dash-pot is connected to the 
top brush-holde-r, aud plunger part to the bottom brush-holder. 
See that the field and regulator wires are connected and that all 
connections are securely made. When all connections have been 
made, make a careful examination of screws, joints, and all mov- 
ing parts. They must be free from stickiness, and not bind in 
any position. 

To determine when the machine is under full load, notice the 
position of the regular armature, which should be within i" of 
the stop. At full load the normal length of the spark on the com- 
mutator should be about -^\'\ If it is less than this, shut down 



182 



HANDBOOK ON ENGINEERING. 



BEST POSITION OF AIR BLASTS AND JETS ON 
LD AND MD DYNAMOS. 




Lift Regulator as high as possible. 

Figs. 11 and 12. 



HANDBOOK ON ENGINEERING. 183 

the machine and move the commutator forward, or in direction of 
rotation until the spark is of the desired length. If the spark is 
too long, move the commutator back the proper amount. 

DIRECTIONS FOR SETTING THE AIR BLAST JETS ON LD AND 
MD DYNAMOS. 

With new segments* — Loosen bolts A-A-A-A and turn the 
air-blast so as to bring the bolts in the centers of the slots 
B-B-B-B. Set the brushes by the gauge. Lift the regulator 
lever as high as possible and set the point D of the air blast jet 
-^^" in front of the point P of the brush A. Place the lower jet 
in the same relative position with the lower brush. 

As segments wear down* — Loosen the bolts A-A-A-A and 
follow up the wear of the segments by turning the air blast against 
direction of rotation of armature as indicated. Turn the point 
of the jet downward, so as to blow more directly through the slot 
between the segments. Set the lower jet in the same relative 
position with the lower brush. 

DIRECTIONS FOR SETTING THE AIR BLAST JETS ON E, H, 
K, L AND M DYNAMOS. 

With new segments* — Set the brushes by the gauge. Lift 
the regulator as high as possible, and set the point D of the jet in 
line with the point P of the brush. Keep a space of gL" between 
the jet and the segment. 

As segments wear down* — Loosen the bolts A-A-A-A and 
follow up the wear of the segments by turning the air blast against 
direction of rotation of armature, as indicated. Turn the point 
of the jet downward, so as to blow more directly through the slot 
between the segments. Set the lower jet in the same relative 
position with the lower brush. 



184 



HANDBOOK ON ENGINEERING. 



BEST POSITION OF AIR BLASTS AND JETS ON 
E, H, K, L AND M DYNAMOS. 



With new sebmbnts. 




Lift Regulator as high as possible. 
Figs. 13 and 14. 



HANDBOOK ON ENGINEERING. 



185 



THOMSON=HOUSTON ARC DYNAMOS TO RUN LEFT=HAND OR 
CLOCKWISE, FACING COMHUTATOR. 

In changing over a T-H dynamo from right-hand to left-hand, 
the following new parts, which are made specially for left-hand 
machines, must be ordered : — 







MD2 


and LD2. 






Quantitj^. 










Cat. No 




Air Blast with Back Plate and 


jets 


. 1525 




Yokes with equalizer bar and link . 


. 1571 




Brush-holder 


Posts 






. 1799 




c( 


t4 






. 1800 




Regulator 








. 1733 



MD12 and LD12. 

Same as for MD^ and LD^ except : 

Regulator (for MD12) 

Regulator (for LD12) .... 



2121 
1813 



K^ L2 andM2. 



Air Blast with Back Plate and Jets 
Yoke 



. 1523 

. 1543 

"... .?^^% 1544 

Adjustable connection 1559 

Brush-holder posts 1787 

" . 1788 

Regulator 1729 

Ki2andMi2. 



Same as K^ and M^ except : 
1 Regulator 



1726 



186 



HANDBOOK ON ENGINEERING. 



In case it should be preferred to change over the right-hand 
regulator so that it could be used on left-hand machine, the fol- 
lowing instructions should be followed : — 

The regulator should be taken apart and reassembled with 
" supporting arm " projecting from the proper side of regulator, 
to allow of bolting to the right-hand side of generator frame. 
Holes for this purpose should be laid out with a regulator in place, 




Arc Generator Arranged for Left-hand Rotation. 
Fiff. 15. 



drilled in any convenient manner (usually with a ratchet) and 
tapped. Holes should also be drilled and tapped on right-hand 
side of frame for the vulcanite block which carries the binding 
post for the field and regulator wires. 

The cut-out is set in precisely the same manner as with right- 
hand machines. 

The commutator is set in the following manner (see Figs. 
9 and 10) : After setting the brushes accurately to gauge for 
brushes, turn the armature so that the lead wire of No. 1 coil is 



HANDBOOK ON ENGINEERING. IS? 

on top. Then turn the armature in the direction in which it is to 
rotate until No. 1 coil just appears under right held. Now set the 
commutator with segment No. 1 corresponding in position with 
coil No. 1 and set the lead on segment No. 3. The commutator 
may then be secured in place and the machine started up in the 
usual manner. 

The controller will now be on the negative side of the machine, 
whereas, before it was on the positive side. If it is desired to 
keep the controller side positive, it will be necessary to remag- 
netize the fields so that the right field will attract the north end 
of a compass needle. 

SOME TROUBLES WHICH HAY BE MET AND THEIR CAUSES- 
REVERSAL OF POLARITY. 

Cases are frequently reported where generators, from lightning 
discharges, wrong plugging on switch-board, or some other 
reason, suffer a reversal of polarity. The effect of reversal is 
that the lamps in circuit with the machine burn ' ' upside down ; ' ' 
that is to say, the lower carbon becomes positive, which has the 
effect of throwing much of the light up instead of down, and with 
some carbons the arc will flame badly. This can be remedied 
temporarily^, by changing the plugs on the switch-board, so that 
the current will enter the line where ordinarily it returns. 

Occasion should be taken, however, the following day, or as 
soon thereafter as possible, to properly magnetize the fields so 
that they will be the right polarity. This may be done as fol- 
lows : — 

Close the armature short circuiting switch on the frame of the 
machine and run a loop from some other arc generator which 
happens to be in operation. Connect the positive side of this loop 
to the lower binding post .^on the right leg of the machine, and 
the negative side of the binding post P^ q^ the end of the frame 



188 HANDBOOK ON ENGINEERING. 

under the regulator, see Fig. 2. Then open the armature short 
circuiting switch on the second generator. A very few seconds 
will suffice to correctly polarize the first machine. Sometimes 
one or more layers of the field winding may become short circuited 
by lightning discharge or by the dropping of water or oil on 
them. A machine with such a field will not carry its load without 
flashing. 

To detect a short circuit in the field, make all adjustments as 
if working under normal conditions, then run the machine at the 
proper speed on a dead short circuit. If there is no short circuit 
in the field, the armature of the regulator will be drawn up hard 
against the bottom of the magnet, but if there is a short circuit in 
the field the armature will drop more or less according to the 
amount of field wire cut out of circuit. 

To find out which half of the field is affected, close the field 
switch and remove the regular wire from the Post P^, Fig. 2, then 
connect posts P^ and N to some source of direct current, as a 
110-volt exciter, and with a volt-meter measure the drop in 
voltage between posts N and xi^ and between A and P^. The 
drop should be very nearly the same in both cases if the winding 
is perfect, but the drop will be less across that field which is short 
circuited. If an ammeter is at hand, readings of the current 
and voltage may be taken, from which the resistances can be 
easily calculated. 

The resistances of one single field of the various machines are 
ffiven below : — 





COLD 




COLD 


CLASS. 


RESISTANCE. 


CLASS. 


RESISTANCE 


K2 . . 


. . . 3.40 


P2 . . 


. . 7.50 


K12 . . 


. . . 6.60 


LD2 


. . 7.00 


L2 . . 


. . . 5.50 


LD12 . 


. . 12.00 


M2 . . 


. : . 5.80 


MD2 . 


. . 5.75 


M12 . . 


. . . 14.00 


MD12 . 


. . 13.60 



HANDBOOK ON ENGINEERING. 189 

Another trouble which is liable to be met is flashing. When a 
generator flashes an arc is drawn around, the commutator from 
one brush to the other, which soon short circuits the armature, 
putting out the lights. This arc is usually broken very quickly, 
but the flashing may be repeated at frequent intervals, There 
are several causes of flashing, such as overload, low speed, sticki- 
ness in the regulating mechanism, short circuit in the field, com- 
mutator not in proper position, or a dash-pot which is too stiff or 
too loose. If a machine flashes when running under proper 
load and at proper speed, see that there is no stiffness in the 
regulating mechanism, then examine the cut-out and note the 
length of the spark, which should be about -^q" long at full 
load. 

If all these adjustments are right, make the test described 
above for a short circuit in the fields. 

RING ARMATURES. 

All K^ M, LD and MD machines are now made with ring- 
armatures, which are a great improvement over the old st^de 
armature in that they have better ventilation, higher insulation, 
greater freedom from burning out and improved facilities for 
removing faulty coils and substituting new ones. 

A recent improvement in the construction of these armatures 
consists in the removal of all insulation from the cores and the 
addition of more insulation to the separate coils. The cores are 
divided into three sections' with ventilating spaces between. 
Armatures which are constructed according to this method run 
much cooler than the older forms. By removing the insulation 
from the cores these new coils may.be applied to any of the older 
armatures now in use. 

These armatures are interchangeable with the old style armatures, 
and can be used in au}^ of the machines mentioned on page 185. 



190 



HANDBOOK ON ENGINEERING. 









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DC 



HANDBOOK ON ENGINEERING. 



191 



111 case it becomes necessary to remove a faulty coil, the following 
directions should be carefully followed : — 






ttlv: 



Hi 



Armature Core and Winding. 
Fio-. 17. 




Armature Spider and Shaft. 
Fio-. 18. 



DIRECTIONS FOR PLACING COILS IN RING ARMATURE 
WITH INSULATED CORE. 

After the armature has been taken out of the machine, remove 
the brass binding wire by cutting the bands with a hack-saw or 



.192 HANDBOOK ON ENGINEERING. 

file, carefully covering all the exposed parts of the arroature with 
a cloth, so as to prevent filings from lodging on the winding. 
Carefully remove the insulating bands, as they can be used again 
in rebinding the armature. Remove the cord and the tape from 
the joints of the lead wires and cross connections, at each end of 
the armature. Take out the lead wires and remove the wooden 
disks from the shaft. These disks are held in place by a set- 
screw, passing through a brass piece let into the disk, and resting 
on the shaft. Unsolder the joints on the coils that are to be 
removed. Take out the bolts holding the two gun-metal spiders 
together, and with a long steel j^in or drift, drive out the key, 
which fastens the loose spider to the shaft ; the loose spider is on 
the commutator end. The spider next to the pulley is securely 
fastened to the shaft hy a steel pin drawn tightly into a reamed 
hole, passing through both spider and shaft. By driving on the 
commutator end of the shaft with a hard-wood block and mallet, 
or lead hammer, the shaft with the fixed spider may be removed, 
and the remaining loose spider can then be driven out with the 
hard-wood block and mallet. Before removing the shaft and 
spiders, note the position of the wedge in the armature core, its 
position is always indicated by the letter W, plainly stamped on 
the hub of the loose spider. 

Remove the vvood spacing blocks, slip the coils around on the 
core until the imperfect coils are over the wedge, then spread these 
coils apart so as to expose the wedge, and cut away the insula- 
tion on the core for a space of 3|" on top and bottom, over the 
space containing the wedge ; the wedge may then be driven 
towards the center of the core, taking care that it does not 
drop on the coils opposite and injure them. The faulty coils 
may now be removed, new ones be inserted and the wedge 
be replaced and very carefully reinsulated. This insulation 
is put on, l>eginniiio- with the layer next to iron core, as fol- 
lows : — 



HANDBOOK ON ENGINE EKING. 



193 



(1) 1 layer of paper, 

(2) 1 layer of mica, 

(3) 1 layer of sheeting, 

(4) 1 layer of tape, 



(5) 1 layer of mica, 

(G) 1 layer of canvas, 

(7) 1 layer of tape, 

(8) 1 layer of paper. 



On armatures with bare cores the insulation given above is, of 
course, not used. 

While tvorking on the annature it should rest upon a mattress 
or bag of -waste on the foor^ so as to avoid any injury to the coils. 




Fig. 19. 



As shown ill Fig. 19, the insulation of the wedge should break 
joints with the insulation of the body of the core ; i. e., on a line 
1" to I" from a cut half through and remove the insulation, then 
insulate the space c c one-half the regular thickness, and the 
space h b the remaining half. This will break joints and prevent 
any possibility of a contact through the opening caused by cut- 
ting away the wedge insulation. 

13 



194 HANDBOOK ON ENGINEERING. 

Slip the coils around to their proper places, so that they will 
be in correct position with regard to the arms of the spiders. 

The loose spider ^ay now be j^ut in place and afterwards the 
fixed spider and shaft, the bolts being inserted and the nuts 
tightened up. Replace the key in the loose spider, put on the 
wooden disks and carefully solder and tape all the joints of lead 
wires and cross connections. Replace the spacing blocks in their 
proper positions, solder and tape the connections, and the arma- 
ture is ready to be bound. This can best be done in a lathe, but 
the armature may be mounted in the regular dynamo legs, set out 
on the floor and the power applied either by hand or any other 
convenient method. 

The binding wite used is No. 11, hard brass. The arrange- 
ment of the binding wire is clearly shown in the original bands of 
the armature and should be carefully noted before they are 
removed. The same brass clips may be used again, provided due 
care is taken in bending up the ends, when the old band is taken 
off, 

SWITCHBOARDS. 

The standard arc lighting switchboard consists of a marble 
panel, to the back of which the conductors are attached. When 
very large boards are built they are made by combining several 
panels. Switchboards of any capacity can be constructed without 
difficulty. The general arrangement of conductors is the same 
for all sizes. 

Each panel is drilled with counter-sunk holes arranged in 
rows, and in each hole, a brass bushing is fitted. All the bush- 
ings of the same horizontal row on the right of the center of the 
panel are electrically connected , except those of the bottom row, 
and a similar connection is made between the bushings on the 
left of the center. A heavy brass strap is supported by the back 
of the panel behind each vertical row of holes and has biishings 



HANDBOOK ON ENGINEERING. 



195 



in it corresponding to those in tlie faoe of the j^anel. These 
straps are placed several inches back of the marble, but any one 
of them can be put in electrical connection with any horizontal 
conductor it crosses by the use of suitable brass plugs inserted in 
the bushings. 



m 





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e 


d 

c 


Q 


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6 





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Q- :r/^ 





Standard Plug Switchboard for 6 Circuits. 
Fig. 20. 



In a standard panel the number of horizontal rows of holes 
equals one more than the number of generators. The vertical 
rows are always twice the number of generators. The positive 
leads of the generators are attached to binding posts on the left- 
hand ends of the horizontal conductors. The negative leads are 
connected to the corresponding binding posts at the right-hand 
end of the board. 



196 



HANDBOOK ON ENGINEERING. 



The positive line wires are connected to the vertical straps on 
the left, and the negative wires to similar strains on the right of 
the center of the i^anel. 

If a switch board plu^ be inserted in any of the holes of the 
board, it puts the corresponding generator lead and line wire in elec- 
trical connection, but as the 
positive line wires are back of 
the positive generator leads 
only, it is not possible to re- 
verse the connection of the 
line and generator accident- 
ally, though any other com- 
binations of lines and gen- 
erators can be made readily 
and quickly. 

The holes of the lower 
horizontal row have bushings 
connected with the vertical 
straps only. Plugs connected 
in j)airs by flexible cable and 
inserted in the holes put the 
corresponding vertical straps in connection as needed, and nor- 
mally independent lines may be connected when one generator 
is required to supply several circuits. 

Lines and generator leads may be transferred, while running, 
by the use of these cables, without shutting down machines or 
extinguishing lamps. 

The standard hoards are arranged for an equal number of 
generators and circuits, but special boards for any ratio of cir- 
cuits to generators can be built. As it is sometimes convenient, 
even in small plants, to interchange lines and generators without 
shutting down machines, a special transfer cable with plugs has 
been devised. This serves the same purpose as the regular trans- 




Back of Switchboard. 
Fig. 21. 



HANDBOOK ON ENGINEERING. 



197 



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Fio-. 2 2. 



198 HANDBOOK ON ENGINEERING. 

fer cable, but the plugs may be used in any of the holes of the 
switchboard as they are insulated, except at the tip, and when 
inserted connect with the line strips only. 

The transfer of circuits from one generator to another gives 
trouble to dynamo tenders who are not familiar with the operation 
of plug switchboards. Fig. 22 illustrates the successive steps 
for transferring the lamps of two independent circuits from two 
generators to one without extinguishing the lamps on either cir- 
cuit. This process is a very simple example of switchboard 
manipulation, but illustrates the method used for all combinations. 

The location of plugs is shown by the black circles, which 
indicate that the corresponding bars of the horizontal and vertical 
rows are connected. 

Circuits No* i and 2, running independently from generators 
No. 1 and No. 2 respectively, are to be transferred to run in 
series on generator No. 2. 

In A, Fig. 22, are two circuits running independently. In B, 
the positive sides of both generators and circuits are connected by 
the insertion of additional plugs. 

At C both generators and circuits are in series. 

Before passing- from C to D, raise the generator arm of No. 1 
generator slowly until it reaches the top, and all of the load of 
this machine is transferred to No. 2. Close the armature short- 
circuiting switch No. 1, cutting the generator out of action. 
Next, insert jolugs and cable as shown in D. Then withdraw 
plugs on row corresponding to generator No. 1 and the circuits 
No. 1 and No. 2 are in series in machine No. 2, and machine 
No. 1 is disconnected as at E. 

Similar transfers can be made between any two circuits or 
machines and by a continuation of the process, additional circuits 
can be thrown in the same machine. The transfer of the two 
circuits to independent generators is accomplished by reversing 
the process illustrated. 



HANDBOOK ON ENGINEERING. 

L'oe 



199 



Resistance 



wm 



O I fn i 



-^ 



i 



Si 



^ IT 

(^^J" Ua m OS "Q 



METER FOR 4 to 8 LAMPS. 



T 



■WKftf liliSCS, 



Resis-taric© 



Geoera-bor 



ji' 



ip 



/"^ 



METER FOR STATION USE. 
CONNECTIONS FOR WATT-METERS FOR SERIES ARC CIRCUITS^ 

Fia:. 23. 



200 HANDBOOK ON ENGINEERING. 

WATT=METERS. 

Watt-meters are now built to measure the power supplied on 
series arc circuits. These watt-meters are similar in principle 
to those used on incandescent lighting sj'^stems, and, being ex- 
tremely accurate, are ecjually effective in preventing waste of 
current. The watt-meters supplied to customers are made in 4 
lamp or 8 lamp capacities. An excess of voltage equivalent to 
two lamps over the rated load causes the meter to automatically cut 
out, both lamps and meters being short-circuited. This prevents 
the interruption of the series circuit in case of any local trouble 
with lamps or line inside the meter circuit. Station watt-meters 
are arranged to measure the total output of a generator, and are 
made with capacities for 35, 50, 65, 80, 125 or 150 lamps. 

INSTRUCTIONS FOR THE INSTALLATION AND CARE OF ARC 
LAMPS. 

The lamps should be hung from the hanger boards provided 
with each lamp, or from some suitable supports of wire or chain. 

As the hooks on the lamp form also its terminals, they should 
be insulated, where a hanger board is not used, from the chains or 
wires used to support the lamp. 

To make the upper carbon positive, the wire from the positive 
terminal of the machine should be fastened into the binding post 
hook, on the switch side of the D lamp, and on the opposite side 
in the M and K lamps. When the lamps are hung where they 
are exposed to the weather, they should be covered with a metal 
hood, to prevent injury from rain or snow. In such cases 
care should be taken that the circuit wires do not form a contact 
on the metal hood, and short-circuit the lamp. Before the lamps 
are hung up, they should be carefully examined to see that the 
joints are free to move, and that all connections are perfect. 



HANDBOOK ON ENGINEERING 



201 



No lamp should be allowed to remaiu in circuit with the 
covers removed and mechanism exposed. Such practice is 
dangerous. 




Interior of M Arc Lamp. 
Fio-. 24. 



STARTING THE LAMPS. 

When the lamps are all in position and ready for operation, 
the machine may be started, and when the armature has reached 



202 



HANDBOOK ON ENG1NEERTN(} . 



its proper speed, the short-circuiting switch on the frame should 
be opened. 




^"^r- 



CONNECTIONS FOR M AND K ARC LAMPS. 

Fi^. 25. 



This method allows the generator to take up its load 
gradually, and is a very important point in the handling of the 
machine, particularly when series incandescent lamps are in the 
circuit. 



HANDBOOK ON ENGINEERING. 203 

The generator should be driven at its proper speed, as desig- 
nated by the maker. The regulator lever will first rise and then 
oscillate slowly up and down for short distances, as the regulator 
is cut in and out by the controller magnet. If the movements are 
too great, the lights will vary in intensity — first up, then down. 
This condition will result from a weakness of the regulator dash- 
pot. The regulator lever should always be a short distance away 
from the stop — say from i" to ^" or more, according to condi- 
tions — and should always vibrate up and down in the manner 
stated. Should the lever of the regulator remain down, it shows 
that the speed of the machine is not sufficient to supply the circuit, 
or that the machine is overloaded with lights. 

The controller magnet should be constantly opening and 
closing its contacts. This movement is very slight. The arc of 
the 2000 c. p. lamps should be -f-^" to i" in length and the 1200 
c. p. lamps should have an arc -^~' to ^y in length. If the car- 
bons are of good quality, the arc should not flame or hiss. 



INSTRUCTIONS FOR REPAIRING, TESTING AND ADJUSTING 
ARC LIGHTS. 

It frequently becomes necessary, after the lamps have been in 
use for a considerable length of time, especially when used for 
street lighting, to clean, repair and readjust them. If the parts 
are not complete, additional parts should be ordered by cata- 
logue number and inserted in the lamp. 

After cleaning and repairing, the lamp should be tested and 
readjusted. Experience shows that whenever even one new part 
has been put into a lamp or generator, trouble may result if tests 
and readjustments are not made before putting the apparatus into 
regular service. 

In order to properly test the lamps that have been repaired, 
select some part of the engine room where the lamps can be hung 



204 HANDBOOK ON ENGINEERING. 

up and burned without being subjected to drafts of air ; other- 
wise, they may hiss and act badly, no matter how carefully the 
adjustments may be made. 

When the lamps have been hung up and attached to the 
hanger boards, or some similar arrangement for connecting to the 
circuit in the usual manner, the carbon rods should be cleaned 
thoroughly with cotton waste. If any sticky or dirty spots 
appear, which cannot be readily removed with waste, use a piece 
of well-worn crocus cloth, always being careful to use a piece of 
clean waste before pushing the rod up into the lamp. Under no 
circumstances whatever should the rods be pushed up into the 
lamps in a dirty condition ; they should always be cleaned in the 
manner described. 

The tension of the clamp which holds the rod is adjusted by 
raising or lowering the arm at the top of the guide rod. If the 
tension is too great, the rod and clutch will wear badly and the 
feeding will be uneven, causing unsteadiness in the lights. Too 
light tension will not allow the clutch to hold up the rod and any 
sudden jar to the lamp will cause the rod to fall and the light to 
go out. 

The double carbon or M lamp should have the tension of the 
second carbon rod a trifle lighter than the first one. 

When adjusting the tension, be sure to keej) the guide rod 
jjerpendicular and in perfect line with the carbon rod ; it should 
be free to move up and down without sticking. 

The tension of the clutch in the D lamp s'hould be the same as 
that of the K lamp. It is adjusted by tightening or loosening 
the small coil spring from the arm of the clutch to the bottom of 
the clamp stop. 

To adjust the feeding point in the K lamp, press down the 
main armature as far as it will go, then push up the rod about 
one-half its length, let go the armature and then press it down 
slowly, and note the distance of the bottom side of the armature 



HANDBOOK ON ENGINEERING. 205 

above the base of the carved part of the pole. When the rod 
just feeds, this distance should be J". If it is not, raise or lower 
the small stop which slides on the guide rod passing through the 
arm of the clutch, until the carbon rod will feed when the arma- 
ture is I" from rocker frame at the base of the pole. 

To adjust the feeding point of the 3f lamp, adjust the first rod 
as in the K lamp. Then let the first rod down till the cap at the 
top rests on the transfer lever. The second rod should feed with 
the armature at a point ^^" higher than it was while feeding the 
first rod, that is, it should be -f^" from rocker frame at base of 
pole. 

The feeding- point of the D lamp is adjusted by sliding the 
clamp stop up or down, so that the rod will feed, when the rela- 
tive distances of the armature of the lifting magnet and the 
armature of the shunt magnet from rocker frame are in the ratio 
of 1 to 2. There should be a slight lateral play in the rocker, 
between the lugs of the rocker frame. 

Make a careful examination of all joints, screws, wires and 
other parts of the lamps. The ai^matures of all the magnets should 
be central with cores, and conie down squarely and evenly. There 
should be a separation of ^^" between the silver contact points, 
when the armature of the starting magnet is down. This contact 
should be perfect when the armature is up. The arm for 
adjusting the tension should not touch the wire or frame of the 
lamp, when at the highest point. There should be a space of 
A" ^^" i" between the body of the clutch and the arm of the 
clutch, to allow for wear on the bearing surfaces. 

Always trim the lamps with carbons of proper length to cut 
out automatically, that is, have twice as much carbon projecting 
from the top as from the bottom holder. Always allow a space 
of i" when the lamp is trimmed, from the round head screw in 
the rod, near the carbon holder, to the edge of upper bushing, so 
that there will be sufficient suace to start the arc Be careful to 



206 HANDBOOK ON ENGINEERING. 

get the carbons as accurately centered as possible. They will 
generally come right after one or two trials. 

The arcs of the 1200 candle-power lamps should be adjusted 
to^3_"^ with full length of carbon. Arcs of 2000 candle-power 
lamps should be adjusted from ^l" to ^^2" when good carbons are 
used. Lamps should always maintain a fairly even arc. The 
length of the arc will slightly increase as the carbons burn away, 
but they should not hiss, flame, or overfeed at any time. If the 
switch is thrown and the lamp cutoff, and then turned on quickly, 
the upper carbon should " pick up " promptl}^ with a normal arc, 
not hiss over a few seconds, and then burn as quietly as before. 

When the upper catbon rod is drawn up by the hand, the 
lamp should cut out promptly and not " flash " the generator. 
In the case the arc is very long or causes flashing, look at the 
contacts and see that they are clean and make a good square con- 
tact. Also examine the centering of the armature. The cause 
of the trouble will usually be found in one of these places. 

The action of a lamp that feeds badly may often be con- 
founded with that of a badly flaming carbon. The distinction 
can readily be made after a short observation. The arc of a lamp 
that feeds badly will gradually grow long until it flames, the 
clutch will let go suddenly, the upper carbon will fall until it 
touches the lower carbon, and then pick up. A bad carbon may 
burn nicely and feed evenly, until a bad spot in the carbon is 
reached, when the arc will suddenly become long and flame and 
smoke, due to impurities in the carbon. Instead of dropping as 
in the former case, the upper carbon will feed to its correct posi- 
tion, without touching the lower carbon. 

After the lamp has been tested and burns satisfactorily in the 
station, tighten up the adjusting screws, and if necessary, put a 
small amount of thick shellac on the bottom of the guide rod. 
This will prevent the stop from falling, in case the screw which 
holds it becomes loose or broken. The lamps are now ready to 



HANDBOOK ON ENGINEERING. 207 

be placed on the circuit, but if it is necessary to store them, they 
should be put into some part of the building or engine room where 
they will not become covered with dust before they are taken out. 
If they become dusty, use a small hand bellows to blow away the 
dust which may have collected on the working parts of the lamps, 
before placing them on the circuit. 

SUMHARY. 

Ths following' summafy of the foregoing instructions may be 
useful for the guidance of men in charge of dynamos : — 

1. In operating an arc system, attend strictly to all the points 
herein given. 

2. Be sure that the speed of the dynamo is right and that the 
belt has its proper tension. 

3. See that the regulator always works properly, and has suffi- 
cient " surplus " or space between its armature and the stop. 

4. Be careful that all connections of wires are well made. 

5. Do not allow the circuit to become uninsulated at any point. 

6. Keep every part of the machine and lamps scrupulously 
clean . 

7. Keep all the insulations free from metallic dust or gritty 
substances, by a careful cleaning once a day. 

8. Keep the bearings of the machine well supplied with the 
best quality of mineral oil. 

9. Do not use water or ice on a bearing in case of heating, as 
the water is liable to get into the armature and injure the insula- 
tion. 

10. Lubricate the commutator of the C and E machines hK 
touching the surface occasionally with an oiled cloth. 

11. The commutator on the machine is set carefully before 
leaving the factory in the best jjosition for proper working, and 
its position marked by chisel marks on the commutator and shaft, 



208 HANDBOOK ON ENGINEERING. 

If the commutator is ever removed from the machine, it must be 
put back in exactly the same position on the shaft, and the red, 
white and blue leads must be put into the posts marked 1, 2 and 
3 respectively. If wrongly placed, the machine will either not 
generate, or will act very badly. 

12. When the commutator segments become badly worn, they 
may be turned down in a lathe, either by removing the commu- 
tator entirely from the shaft of the machine and putting it upon 
an arbor, or by removing the segments separately and screwing 
them to a jig, which may then be put into the lathe. The use of 
the jig is especially recommended for turning down the segments 
as the adjustment of the commutator is less liable to be changed 
than when the arbor is used. 

13. The durability of the commutator segments will depend on 
the care exercised in the running of the machine. 

14. The brushes must be set carefully by the "gauge for 
brushes," in the manner explained before. 

15. The spark on the tips of the brushes will vary with the set 
and wear of the brushes. It should be from i" to i" long, and 
only on the forward brushes. 

16. The carbon rods in every lamp should be carefully cleaned 
daily. 

17. The carbons should be in perfect alignment and firmly 
clamped in the holders. 

18. If a lamp burns badly and with a bluish flame, or contin- 
ually hisses, it is probably due to j^oor carbons, which should be 
removed and better ones substituted. 

19. The lamps rarely burn as well when first started as after- 
wards. This is principally due to the fact that the carbons 
require a little time to burn to the proper shape. 

20. The automatic regulator prevents the machine from gener- 
ating more than the amount of current required, so that the lamps 
may l)e thrown on or off the circuit at pleasure. 



HANDBOOK ON ENGINEERING. 



209 



21. Do not tamper with adjustments made in the factory. 

22. Do not imagine that every time a lamp hisses or flames a 
httle it is out of adjustment. As a rule, bad working is due to 
stickiness of the moving parts, or to poor carbons. The lamps 
once properly adjusted and operated with good carbons, should 
not get out of adjustment, and should be let alone in that respect. 

2o. If the machine works badly, it should be tested with a mag- 
neto for grounds of connection between the circuit and the frame 
of the machine. The circuit should also be daily tested, and any 
faults found should be immediately remedied, as otherwise they 
will inevitably cause trouble. 

24. All construction and repair work should be done in strict 
accordance with the rules herein laid down. 

TABLE OF MAGNETIZING FORCE IN AMPERE TURNS REQUIRED PER 
INCH OF LENGTH OF MAGNETIC CIRCUIT. 



Magnetic Den- 


MAGNETIZING FORCE IN AMPERE TURNS. 


sity per square 










inch in 

Gausses. 


Air. 


Cast Iron. 


steel. 


Wrouglit Iron. 


5,000 


1,567 


3.80 


2.85 


1.50 


10,000 


3,134 


5.35 


4.25 


2.40 


15,000 


4,701 


6.80 


5.35 


3.20 


20,000 


6,268 


8.00 


6.30 


3.90 


25,000 


7,835 


10.30 


7.50 


4.60 


30,000 


9,402 


16.20 


8.80 


5.30 


35,000 


10,969 


28.70 


10.20 


5.90 


40,000 


12,536 


49.00 


11.70 


6.50 


45,000 


14,103 


80.00 


13.40 


7.10 


50,000 


15,670 


160.00 


15.40 


8.20 


55,000 


17,237 


240.00 


17.80 


9.50 


60,000 


18,804 


350.00 


20.70 


11.00 


65,000 


20,371 


490.00 


24.10 


13.50 


70,000 


21,938 


650.00 


28.00 


17.00 


75,000 


23,505 
25,072 




34.00 
42.00 


21.80 


80,000 




27.50 









210 HANDBOOK ON ENGINEERING. 

THE 5TEAM ENGINE. 

CHAPTER XI. 
THE SELECTION OF AN ENGINE. 

Thete ate so many conflicting statements in regard to the 
merits and demerits of the several engines placed in the market 
that one is often confused in judgment, and scarcely knows how 
to proceed in the matter of selection, 

It is easy to advise that " When you are ready to buy, select 
the best engine, for in the long run the best is the cheapest." 
No one would pretend to deny this as a general rule, yet there are 
circumstances which so materially modify this rule that it would 
seem to a casual observer to be entirely set aside. There are 
localities in which the price of fuel is so low that it scarcely war- 
rants the doubling of the price on an engine to save it ; and in 
such localities the owners usually want an engine of the very 
simplest construction; hence, they almost invariably select an 
ordinary slide valve engine with a throttling governor. This 
selection is made for several reasons, among which are low first 
cost, simple in detail, remoteness from the manufacturer or from 
repair shops. 

For small powers in which it is desirable that the investmeut 
be as low as consistent with commercial success, the engine 
selected should be fitted with a common slide valve ; this will in 
general apply to all engines having cylinders eight inches or less 
in diameter. 

If upon a thorough canvass of the situation, it then be thought 
advisable to employ an automatic cut-off engine, the next ques- 
tion would probably be whether it shall be fitted with a positive, 
or some one of the various "drop" movements now in the 
market. 



HANDBOOK ON ENGINEERING. 211 

For the smaller sizes, say 8 to 24 inches diameter of cylinder, 
it will perhaps be found more desirable to use an automatic slide 
cut-off, of which there are now several varieties offered through 
the trade. This style of engine has the advantage of being low- 
priced, efficient and economical. 

Small engines are usually required to run at prett}^ high 
speed ; there is a very decided advantage in this on the score of 
economy, as a small engine running at a quick speed will be quite 
as efficient as a large engine running at a slow speed, with the 
further advantage that the former will not cost in original outlay 
more than about two-thirds of the latter, while the cost of operat- 
ing will be no greater per indicated horse power. 

The slide valve is still used to the almost total exclusion of all 
other kinds in locomotives. It is doubtful whether a better valve 
for that particular use can be devised. It is simple, efficient, and 
readily obeys the action of the link when controlled or adjusted 
by the engineer. For portable engines and the smaller stationary' 
engines it leaves little to be desired in point of simplicity. 

One objection to a slide valve is that it cannot readily be made 
to cut off steam at, say, half-stroke or less, without interfering 
with the exhaust. In ordinary j)ractice | to | seems to be where 
most slide valves cut off as a minimum, perhaps | would repre- 
sent nearer the actual average conditions. 

It can easily be shown that this is very wasteful of steam, and 
consequently not economical in fuel ; but as there are cases in 
which the loss in fuel is fully gained by other advantages, the 
ordinary slide valve will, in all pro]:>ability, continue to be 
used. 

High speed engines* — Tbe general tendency seems now to be 
in the direction of a horizontal engine with a stroke of medium 
length having a rapid piston speed and a rapid rotation of crank 
shaft, rather than a longer stroke with a less rate of revolution. 
This rapid movement of piston and crank shaft j^ermits the use of 



212 HANDBOOK ON ENGINEERING. 

small fly-wheels and driving pulleys, and thus very materially 
reduces the cost of an engine for a given power. 

To illustrate this, it may be said that a 16 x 48 inch engine 
using steam at 80 lbs. pressure and cutting off i stroke, running 
at the rate of 60 revolutions per minute, may be replaced by 
an engine having a 13x24 inch cylinder, running at the rate of 
200 strokes per minute, the pressure of steam and point of cut- 
ting off remaining the same, both engines being non-condensing, 
and representing the best examples of their kind. The differ- 
ence between 60 and 200 revolutions per minute in millwright 
work is very great, but there is a constantly growing demand for 
an engine which shall meet such a requirement whenever it 
shall present itself ; by this is not to be understood an engine 
which shall be used at either speed indiscriminately, but rather a 
type of engine which shall be economical in fuel, and shall be of 
a kind by which the rate of revolution may be such as to suit the 
millwright's w^ork without loss of economy in working, and with- 
out excessive outlay for the engine itself in proportion to power 
developed. 

Slow speed engines are designed and built from a standpoint 
entirely different from that of high speed engines ; in the former 
case the reciprocating parts are made as light as possible, con- 
sistent with safety. The fly wheelis large in diameter and made 
with a very heavy rim, especially is this the case with auto- 
matic cut-off engines of long stroke and slow^ revolution of crank 
shaft. 

In high, speed engines the reciprocating parts are often of great 
weight, in order to insure the utmost smoothness of running. 
The piston and cross-head are made of unusual weight that at the 
beginning of the stroke they may require a large part of the steam 
pressure to set them in motion ; this absorbing of power at the 
beginning of the stroke is for the purpose of temporarily storing- 
it up in the reciprocating parts that it may be given off at the 



HANDBOOK ON ENGINEERING. 213 

later portions of the stroke, by imparting their momentum to the 
crank ; thus at the beginning of the stroke, ^these reciprocating 
parts act as a temporary resistance, but once in motion they tend 
by their inertia to equalize the pressure on the crank pin, and so 
produce not only smooth running, but a very uniform motion. 

Results to be obtained in pi* actice, — The best automatic non- 
condensing engines furnish an indicated horse power for about 
three pounds of good coal, depending somewhat upon the fitness 
of the engine for the work and the quality of the coal. With a 
condenser attached, a consumption as low as two pounds has been 
reported, but this is an exceptional result , 2i pounds may be 
quoted as good practice. The larger the engine the better the 
showing, as compared with smaller engines. 

For ordinary slide valve engines, the coal burned per indicated 
horse power will vary from 9 to 12 lbs., for the sake of illustra- 
tion, we will say 10 lbs., and that the engine is of such size as 
would require for a year's run $3,000 worth of coal; now, an 
ordinary adjustable cut-off engine with throttling governor, ought 
to save at least half that amount of coal, or say $1,500 per year ; 
if the best automatic engine were employed using 2 J lbs. of coal 
per horse power, a further saving of $750 per year could be 
effected, or between the two extremes $2,250 per 3^ear in saving 
of coal, without interferuig in any way with the power, with the 
exception, perhaj)s, that the automatic engine will furnish a better 
power than the former engine. It is easy to see that it is true 
economy to buy the best engine and pay the extra cost of con- 
struction, if the saving of fuel is an element entering into the 
question of selection. 

The cost of an engine for any particular service is always to 
be taken into consideration, for it is possible to contract for a 
certain saving of coal at too high a price, not simply when paid 
out as the original purchase money, but with this economy of 
fuel, the purchaser may have many vexatious and damaging 



214 HANDBOOK ON ENGINEERING. 

delays caused by the breaking of the automatic mechanism of the 
engine. All such delays which would not have occurred to an 
ordinary or simpler engine, are to be charged against any saving- 
credited to the engine which failed in producing a regular and 
constant power. Take a flouring mill for example, producing 400 
barrels per day ; it is easy to see how a single day's stoppage 
would interfere with the trade and shipment by the proprieters, 
yet it would require a very small break in an engine that would 
require less than a day for repairs. 

This does not argue against high grade engines, but the pur- 
chaser should be certain that the engine when once on its founda- 
tions shall be as free from dangers of this kind as any other 
engine of similar economy. 

There are eng-ines which from their peculiar construction 
appear to be very complex, and this objection is often urged 
against them, while the fact is the complexity is apparent rather 
than real. Take the Corliss engine, for example ; it is doubtful 
whether there is another automatic cut-off engine in successful 
use in this or any other country which has cost less for repairs 
during the last ten or twenty years. It is true it contains a great 
many separate pieces in the valve mechanism, but the pieces 
themselves are simple, durable, eas'ily accessible and always in 
sight. These several parts are not liable to excessive wear, but 
such as there is can be readily adjusted. 

The engines to be ]3referred are those in which the valve 
adjusting mechanism is outside of the steam chest and which is in 
plain sight at all times when the engine is in motion. 

Location of engine. — This will depend upon circumstances, 
but it is far from true economy to place an engine in a dark cellar, 
or in some inconvenient place above ground. The engine as the 
prime mover, should have all the care and attention which may be 
needed to insure regular and efficient working. 

Machinery in the dark is almost sure to be neglected. If the 



HANDBOOK OX ENGINEERING. 215 

design of the building, or the nature of the business, is such that 
the engine must be located underground, there should be some 
provision for letting in the daylight ; the extra expense incurred 
will soon be saved by the order, cleanliness and fewer repairs 
required, following neglect. 

The engine should always be close to, but not in the boiler 
room. Many a high-priced engine has had its days of usefulness 
shortened by the abrasive action of fine ashes and coal dust 
coming in contact with the wearing surfaces. There should always 
be a wall or tight partition between the engine and fire room. 

The foundations for an engine should be large and deep. 
Too many manufacturers in marking dimensions of foundation 
drawings for engines, make them altogether too shallow. The 
stability of an engine depends more on the depth than on the 
breadth of the foundations. Stone should be used for founda- 
tions rather than brick, but if the latter must be used they should 
be hard burned and laid in a good cement rather than a lime 
mortar. If the bottom of the pit dug for the engine foundation 
be wet, or the soil uncertain in its stability, it is a good plan to 
make a solid concrete block about a foot and a half thick, on 
which the foundation may be continued to the top. If such a 
concrete block be made with the right kind of cement it will be 
almost as hard and solid as a whole stone. 

The most economical engine is the one in which high pressure 
steam can be used during such portion of the stroke as may be 
necessary, then quickly cut off by a valve which shall not inter- 
fere with the exhaust at the opposite end of the cylinder, and 
allow the steam to expand in the cylinder to a pressure which 
shall not fall below that necessary to overcome the back pressure 
on the piston. In general, the most successful cut-off engines 
use the boiler pressure for a distance of one-fifth to three-eighths 
of the stroke from the beginning ; at this point the steam is cut 
off and allowed to expand throughout the balance of the stroke. 



21() 



HANDBOOK ON ENGINEERING 



The gain by expansion consists in the admission of steam at a 
pressure much above the average required to do the work, and 
allowing it to follow but a small portion of the stroke, then ex- 
panding to a lower than the average pressure at the end of the 
stroke. The mean effective pressure on the piston is that by 
which the power of the engine is measured ; hence, it follows that 
the higher economy is to be reached, other things being equal, where 
the mean effective pressure on the piston is highest when com- 
pared with the terminal pressure, or the pressure at the end of the 
stroke. In order to get this, a high initial pressure is used ; the 
steam follows as short a distance as possible to keep the motion 
regular under a load, and then expanding down to as near the 
atmospheric pressure as possible. 

The following table exhibits at a glance the performance of a 
non-condensing engine cutting off at different portions of the 
stroke. The initial pressure of steam being in each case eighty 
pounds per square inch. 

CUt-OFF IN PARTS OF THE STROKE. 





1 

10 


2 
10 


3 
10 


4 

10 


5 

10 


Mean effective pressure . 


18 


35 


48 


57 


65 


Terminal pressure . 


11 


20 


30 


39 


48 


Pounds water per h'r per 
H. P. . . . . . 


20 


21 


22 


23 


25 



Fractions are omitted in the above table and the nearest whole 
number given. 

Governon — ^^y automatic device by which the speed of an 
engine is controlled may properly be called a governor. There 



HANDBOOK ON ENGINEERING. 217 

are now two distinct methods by which the steuiii supplied lo an 
engine is thas brought under control. The first is usually applied 
to slide valve engines having a fixed cut-off, and consists in the 
adjustment of a valve by which the pressure of steam in the 
cylinder is increased or diminished in order to maintain a con- 
stant rate of revolution with a variable load. The second device 
consists in a mechanism by which the whole boiler pressure is 
admitted to the cylinder, which is allowed to follow the piston to 
such portion of the stroke as will maintain a regular rate of revo- 
lution ;• the steam is then suddenly cut off at each half revolution 
of the engine, thus furnishing a greater or less volume of steam at 
a constant pressure. Neither of these two varieties of governors 
will act until a change in the rate of revolution of the engine 
occurs, and this change will either admit more or less steam as it 
is faster or slower than that for which the governor is adjusted. 
The commonest form of a governor consists of a vertical shaft to 
which are hinged two arms containing at their lower ends a ball 
of cast iron ; as the shaft revolves the balls are carried outward 
by the action of what is commonly called centrifugal force ; the 
greater the rate of revolution the further will the balls be carried 
outward ; advantage is taken of this property to regulate the ad- 
mission of steam to the engine. The action of the balls and that 
of the valve include two distinct principles and should be consid- 
ered separately ; an excellent valve may be manipulated by an 
indifferent governor and so produce unsatisfactory results ; on the 
other hand, the governor mechanism may be satisfactory in its 
operation, but being connected with a valve not properly balanced, 
is likely to cause a variable rate of revolution in the engine. 

Fly- wheel* — The object in attaching a fly-wheel to an engine 
is to act as a moderator of speed. The action of the steam in the 
cylinder is variable throughout the stroke, against which the rev- 
olution of a heavy wheel acts as a constant resistance and limits 
the variations in speed by absorbing the suri3lus power of the first 



218 HANDBOOK ON ENGINEERING. 

portion of the stroke, and giving it out during the latter portion. ' 
The fly-wheel is simply a reservoir of power, it neither creates nor 
destroys it, and the only reason why it is attached to an engine is 
to simply regulate the speed between certain permitted variations 
which are necessary to cause the governor to act, and to equalize 
the rate of revolution for all portions of the stroke, thus convert- 
ing a variable reciprocating power into a constant rotary one. It 
is considered good practice to make the diameter of the fly-wheel 
four times the length of the stroke for ordinary engines, in which 
the stroke is equal to twice the diameter of the cylinder. This 
may be taken as a fair proportion in engine building, and furnishes 
a wheel sufficiently large to equalize the strain and reduce any 
variation in speed to within very ijarrow limits, if the engine is 
supplied with a proper governor. The greater the number of 
revolutions at which the engine runs, the smaller in diameter may 
be the fly-wheel, and it may also be largely reduced in weight for 
engines developing the same power. 

Hofse-power* — By this term is meant 33,000 pounds raised 
one foot high in one minute. The horse-power of an engine may 
be found by multiplying the area of the piston in square inches 
by the mean effective pressure ; this will give the total 
pressure on the piston ; multiply this total pressure by the 
length of the stroke of the piston in feet ; this will give the 
work done in one stroke of the piston ; multiply this product by 
the number of strokes the piston makes per minute, which will 
give the total work done by the steam in one minute ; to get the 
horse-power, divide this last product by 33,000. From this 
deduct, say, 20 per cent, for various losses, such as friction, con- 
densation, leakage, etc. 

CARE AND MANAQEflENT OF A STEAM ENGINE. 

It is to be sui3i3osed to begin with that the engine is correctly 
designed and well made, and that, after a suitable selection of an 



HANDBOOK ON ENGINEERING. 219 

engine for the work to be done, nothing now leniain.s except 
proper care and management. 

Lubrication* — The first and all-important thing in regard to 
keeping an engine in good working order is to see that it is 
properly lubricated. This does not imply, neither is it intended 
to encourage, the use of oil to excess ; all that is needed is simply 
a film of oil between the wearing surfaces. It is marvelous how 
small a quantity of oil is required when of good quality and con- 
tinuously applied. There are several self -feeding lubricators in 
the market which have been tested for years and are a pronounced 
success ; these include crank-pin oilers, in which the oscillatory 
motion of the oil makes a very efficient self -feeding device, the 
flow being regulated by means of an adjustable opening to the 
crank-pin, or in the adjustment of a valve by which its lift is reg- 
ulated by each throw of the crank ; and in others by a continual 
flow through a suitable tube containing a wick or other porous 
substance. For stationary engines, it is desirable that the main 
body of the oiler be made of glass that the flow of oil may be 
closely watched and adjusted accordingly. For the reciprocating 
and rotary parts of the engine, a modification of the above men- 
tioned oilers may be used. They are of various patterns and 
devices and many of them very good. It is also a good plan to 
have some device by which the cross-head at each end of each 
stroke will take up and carry with it a certain amount of oil ; for 
the lower half of the slide this is not difficult to arrange ; for the 
upper side an automatic feeder placed in the middle of the slides 
will provide ample lubrication. 

For oiling the main bearing there should be two separate 
devices, one an automatic glass oiler; and in addition, a large 
tallow cup attached to the cap of the bearing. This cup should 
be filled with tallow mixed with powdered plumbago ; the open- 
ings from the bottom of the cup to the shaft should be not less 
than quarter-inch for small engines, and three-eighths to half -inch 



220 HANDBOOK ON ENGINEERING. 

for larger ones ; so long as the main bearing runs cool the tallow 
will remain in the cup unmelted; but if heating begins, the tallow 
will melt and run down on the surface of the revolving shaft, and 
thus provide an efficient remedy when needed. For oiling the 
valves and piston, a self -feeding lubricator should be attached to 
the steam pipe ; this by a continuous flow of oil will be found not 
only satisfactory m its practical working, but economical in the 
use of oil. 

In selecting an oil for an engine, it is in general better to use a 
mineral rather than an animal oil, especially for use in the valve 
chest and cylinder. The objection to an animal oil, and espe- 
cially to tallow or suet, is that it decomposes by the action of heat, 
often coating the surface of the steam chest, the piston ends and 
the cylinder heads with a deposit of hard fatty matter ; or forms 
into small balls not unlike shoemaker's wax. There is no such 
decomposition and formation in connection with mineral oils, 
which may now be had of uniform quality and consistency, and 
at much lower prices than animal oils. 

The slide valve should be kept properly set and should be 
examined occasionally to see that the face and seat are in good 
condition. So long as this is the case, the valve mechanism and 
the valve itself must be let alone and not tampered with. 

The piston packing will need looking after occasionally to 
see that it does not gum up and stick fast, which it is very likely 
to do when the cylinder is lubricated with tallow or animal oil. 

The rings should fit the cylinder snugly and should be under 
as little tension as possible and insure pevtect contact. If the 
rings are set out too tight they are liable to scratch or cut the 
cylinder; if too loose, the steam will blow through from one end 
of the cylinder, past the piston and into the other. In adjusting 
the springs in the piston, care must be exercised that the adjust- 
ments are such as will keep the piston rod exactly central, to 
prevent sj^ringing the rod, or causing excessive wear on the stuf- 



HAND BOOK ON ENGINEERING. 221 

ting box. There are several packings which do not require this 
adjustment, the rings being narrow, and either expanding by 
their own tension or by means of springs underneath. The only 
thing to be done with such a packing. is to keep it clean, and 
when lubricated with a mineral oil this is not a difficult matter. 
If it groans, t^ke rings out and file sharp edges off. 

The stuffing- boxes whether for the piston or valve-stem need 
to be looked after carefully, and to prevent leaking, will require 
tightening from time to time. There are several kinds of ready- 
made packings in the market, containing rubber, canvas, garlock, 
soapstone, asbestos and other substances which form the basis of 
a good durable packing. These can be had in sizes suitable for 
all ordinarj^ purposes, and their use is recommended. In the 
absence of any of these, a packing made of clean manila or hemp 
fiber will serve a useful purpose. Formerly it was the only sub- 
stance used, but is being gradually superseded by the other kinds 
mentioned above. In packing the small and delicate parts, such 
as a governor stem, a good packing is made by pleating together 
three or more strands of cotton candle-wick. This is soft, pliable, 
free from anything like grit, and will not get hard until soaked 
with grease and baked into a brittle fiberless substance not easily 
described. 

Crank-pins, — There are few things more troublesome to an 
engineer than a hot crank-pin, and it is sometimes very difficult 
to get at the real reason why it heats. Among the principal rea- 
sons for heating are : the main shaft is not " square " with the 
engine, or, that the pin is not properly fitted to the crank; or, 
perhaps, it is too small in diameter — defects which are to be 
remedied as soon as practicable. Heating is often caused by tlie 
boxes being keyed too tightly, or by insufficient lubrication. 
There are now several good self -feeding lubricators in the market 
which willsupply the oil to a crank-pin continuously; these are 
recommended rather than the old style of oil cup, which was 



222 HANDBOOK ON ENGINEERING. 

not only uncertain, but doubtful in its action. Many trouble- 
some crank-pins have been cured of heating by this simple matter 
of constant lubrication. When the crank-pin is rather small for 
the engine and the load variable, there is a possibility of having 
a hot pin at any time ; it is advisable to have ready some 
simple and effective expedient to be applied when it does occur ; 
for this there is perhaps nothing better and safer than a mixture 
of good lard oil and sulphur. 

Connectingf rod brasses, — In quick running engines the 
brasses should be fitted metal to metal ; or, if this is not desir- 
able, several strips of tin or sheet brass should be inserted be- 
tween them and keyed up tight. This gives a rigiditj^ to a 
joint which is difficult to secure when the brasses have a certain 
amount of play in the strap. It is a common practice to bore the 
brasses slightly larger than the pin, so that when fitted to it the 
hole shall be slightly oval, and thus permit a freer lubrica- 
tion than is secured by a close fit around the whole circum- 
ference. 

Knocking* — There are several causes which, combined or 
singty, tend to produce knocking in steam engines. In most 
cases the difficulty will be found to be in the connecting rod 
brasses ; but whether in the crank-pin end or at the cross-head is 
not easily determined in all cases. A very shght motion will 
often produce a very disagreeable noise ; the remedy is, in most 
cases, very simple, and consists in simply tightening the brasses 
by means of the key or other device that may have been pro- 
vided for their adjustment. In adjusting a key it is the common 
practice to drive it down as far as it will go, marking with a 
knife blade the upper edge of the strap, then drive the key back 
until it is loose ; after which drive it down again, until the 
line scratched on the key is within J or i inch of the top of the 
strap. The size of the strap joint and the judgment of the i3er- 
son in charo^e must decide the best distance. This mav be done 



HANDBOOK ON ENGINEERING. 223 

at both ends of the coiiuectiug rod. On starting the engine, the 
cross-head and crank-pin must be carefully watched, and upon 
the slightest indication of heating, the engine should be stopped 
and the key driven back a little further. A slight warmth is not 
particularly objectionable, and will, as a general thing, correct 
itself after a short run. Knocking is sometimes occasioned by a 
misfit, either in the piston, or cross-head and the piston rod. 
These connections should be carefully examined, and under no 
circumstances should lost motion be permitted at either end of 
the piston rod. 

If the means of securing are such that the person in charge can 
properly fasten the piston to the rod, he should see that it is kept 
tight ; if not, then it should be sent to the repair shop at once, as 
there is no telling when an accident is likely to overtake an engine 
with a loose piston. 

The connection between the piston-rod and cross -head is usu- 
ally fitted with a key and furnishes a ready means of tightening 
the joint, if proper allowance has been made for the draft of the 
key. In case there has not, the piston-rod and cross-head should 
be filed out so that the draft of the key will insure a good tight 
joint when driven down. 

The main beanng should be examined and if there should be 
too much lateral movement of the shaft, the side boxes might 
then be adjusted until the shaft turns freely, but has no motion 
other than a rotary one. The cap to the main bearing should also 
be carefully examined, as it may need screwing down and thus 
prevent an upward movement of the shaft at each stroke ; this 
applies more particularly to quick running engines. 

Engines which have been in use for some time are likely to have 
a knock caused by the piston striking the head. This is brought 
about by having a very small clearance in the cylinder and in not 
providing, by suitable liners, for the wear of the connecting rod 
brasses. In a case of this kind, liners should be inserted behind 



224 HANDBOOK ON ENGINEERING. 

the brasses in the conuecting rod, or uew brasses put in, which 
will restore the piston to its original position. 

Knockingf inay be caused by defects in the construction of the 
engine ; such, for example, as not being in line, the crank-pin not 
at right angles to the crank, the shaft may be out of line, etc. 

Whenever the cause is one in which it can be shown that it is 
a constructive defect, there is but one remedy, and that is the re- 
placing of that part, or the assembling of the whole until 
perfect truth is had in alignment of all the parts. This will 
require the services of an experienced engineer but all improperly 
fitting pieces should be replaced by new ones as a safeguard 
against accident, which is likely sooner or later to overtake badly 
fitting pieces. 

If the boiler is furnishing wet steam, or priming, so as to force 
water into the steam pipe, it will collect in the cylinder and will 
not only cause knocking, but on account of its being practically 
incompressible there is danger of knocking out a cylinder head, 
bending the piston-rod, or doing other damage to the engine. 
The cylinder cocks should be opened to drain any collected water 
away from the cylinder. 

Repairs* — Whenever it is necessary to make repairs the work 
should be done at once ; oftentimes a single day's delay will in- 
crease the extent and cost fourfold. If an engine is properly 
designed and built, the repairs required ought to be very trivial 
for the first few years it is run, if it has had jjroper care. It may 
be said in reply to this " true, but accidents will happen in spite 
of every care and precaution." That accidents do occur is true 
enough ; that they occur in spite of every care and precaution is 
not true. In almost every case, accidents may be traced directly 
back to either a want of care, negligence, or to a mistake. 

Fitting slide-valves. — The practice of fitting a slide-valve to 
its seat by grinding both together with oil and emery, is wrong 
and should never )>e resorted to. The proper way to fit tlie sur- 



HANDBOOK ON ENGINEERING. 225 

faces is by scraping ; this insures a more accurate bearing to 
begin with, and will also be entirely free from the fine grains 
of emery which find their way and become imbedded in the 
pores of the casting, and are thus liable to cut the valve face and 
destroy its accuracy. The scraping of the valve and seat has a 
beneficial effect by causing the removal of the fine particles of 
iron, which are loosened by the action of the cutting tool in the 
planing machine, and which ought to be fully removed before the 
engine leaves the manufacturers' hands. Aside from this, it is 
doubtful whether the scraping amounts to an3^thing practically, 
fertile reason that the cylinder and valve are fitted cold, and their 
relative positions are distorted by the action of the heat of the 
steam, once the engine is in use. The scraping which simply 
renders the valve face and seat smooth and hard is all that is 
sufficient to begin with, and may be re-scraped after the valve 
has been in use a few days, should it be found necessary, 
which will not often be the case in small and ordinary sized 
engines. 

Eccentric straps are likely to need repairs as soon as any- 
thing about an engine. They should be carefully watched at 
all times. If they are likely to run hot, it is also probable 
there is more or less abrasion or cutting going on, and if 
prompt measures are not taken to arrest it, they are likely to 
cut fast to the eccentric, and a breakage is sure to occur. 

When the straps begin to heat, the bolts should be slackened 
a little, and at night, or perhaps at noon, the straps should be 
taken off and all cuttings carefully removed with a scraper 
(not with a file) ; the rough surfaces on the eccentric should 
be removed in the same manner. 

The straps should be run loose for a few days, gradually 
tightening as a good wearing surface is obtained. 

The main bearing-^ if neglected, is a very troublesome journal 
to keep in order. The repairs generally needed are those which 

15 



226 HANDBOOK ON ENGINEERING. 

attend overheating and cutting. The shaft, whenever possible, 
should be lifted out of the bearing, and both the shaft, bottom of 
main bearing and side boxes, carefully scraped and made perfectly 
smooth. It sometimes occurs that small beads of metal project 
above the surface of the shaft which are often so hard that neither 
a scraper nor file will remove them ; chipping is then resorted to 
and the fitting completed with a file and fine emery cloth. 

Heating of joittnals* — A very common cause for the heating 
of journals having brasses and boxes composed of two halves, is 
that both halves alter their shape from causes attending their 
wear. Thus, most engineers will have noticed that, although 
there is no wear between the sides of a brass and the jaws of a 
box, yet in time the brass becomes a loose fit in the box. Now, 
since the sides of the brass have, when fitted, no movement in the 
box, it is evident that this cannot have proceeded from wear be- 
tween those surfaces, and it remains to find what causes this 
looseness. Most engineers will also have observed that though 
the bottom or bedding surfaces of a brass and of the box may 
have been carefully filed to fit each other when new, yet if in the 
course of time the brasses be taken out and examined, and more 
especially the bottom brass that receives the weight, the file marks 
will 'become effaced on all parts where the surfaces have bedded 
together well, the surface having a dull bronze and condensed 
appearance. This is caused by the vibrations under pressure hav- 
ing condensed the metal. Now, this condensation of the metal 
moves or stretches it, and causes the sides of the brass to move 
away from the sides of the box, and, consequently, to close upon 
the journal, creating excessive friction that msiy often, and very 
often does, cause heating. It is for this reason that on such 
brasses the sides of the l^rass boxes are, by a majority of engi- 
neers, eased away at and near the joint, and it follows from this 
cause the same easing away is a remedy. 

Govetnof* — It not infrequently occurs that after an ordinary 



HANDBOOK ON ENGINEERING. 227 

throttling eugiue has been used a few years, the speed becomes 
variable to such a degree that it interferes with the proper run- 
ning of the machinery. This occurrence can generally be traced 
directly to the governor. When it does occur, the governor 
should be taken apart and thoroughly examined ; if the needed 
repairs are such as can be easily made in an ordinary repair shop, 
they should be made at once ; if not, a new governor should be 
purchased. The price of governors is now so low that it is better 
and more economical to buy a new one than lose the time and 
pay the bills for repairing an old one. 

AUTOMATIC ENGINES. 

In the care and management of this class .of engines, it is diffi- 
cult to say just what particular attention they need, owing to the 
varietj^ of stjdes and the peculiarities of each. As a rule, how- 
ever, they require first, to be kept well oiled ; second, to be kept 
clean ; third, to be kept well packed ; and fourth, to be let alone 
nights and Sundays. There is little doubt that there has been 
more direct loss resulting from a ceaseless tinkering with an 
engine than results from legitimate wear and tear to which the 
engine is subjected. The writer does not wish to be understood 
as saying that builders of this class of engines are infallible ; it 
might be difficult to prove any such assertion in case it was made ; 
but it may be said with truth, that the engines of this class now 
in the market are carefully designed, well proportioned, of good 
materials and workmanship, and as examples of mechanism are 
entitled to take very high rank. The writer knows of several 
engines of this class which have not cost their owners for repairs 
so much as five dollars in five years' constant use. It is essential 
to the economical working of these engines that the cut-off 
mechanism be in good order and properly adjusted. Whenever 
the valves need resetting, the final adjustment should be made 



228 HANDBOOK ON ENGINEERING. 

with a load on the engine and with the indicator attached to the 
cylinder, the valves being set by the card rather than by the eye. 
No general rule can be given for setting the valves, as the prac- 
tice varies with the size and speed of the engine ; nor is any rule 
needed, for the indicator will furnish all the data required. The 
adjustments may then be made so as to secure prompt admission, 
sharp cut-off, prompt release, and the proper compression. 

TO FIND THE DEAD CENTERS. 

When setting the valve of an engine by measuring the lead, as 
is the usual method, it is necessary that the crank be accurately 
placed on the dead centers at each end of the stroke. Sometimes 
an engineer, when adjusting the valves of his engine, will attempt 
to place the crank on the dead center by watching for the point 
at which the travel of the cross-head stops, or by the appearance 
of the connecting-rod as related to the crank. These methods are 
totally unreliable for obtaining accurate results, especially the 
first one mentioned. The travel of the cross-head and the piston 
near the point of reversal of motion is very slow when compared 
with the valve. The velocity of travel of the valve is at nearly 
its maximum amount when the crank is on the dead center, and a 
slight error in finding the dead center point makes a very appre- 
ciable error in the position of the valve, with a subsequent error 
in its jjroper setting. 

There are several methods for finding the dead center. The 
method that can be recommended and the one that should always 
be used when the dead center of an engine is to be found is that 
familiarly known as " tramming." The dead centers when found 
by this method, are geometrically accurate, no matter if the engine 
is out of level or if the shaft is above or below the axis of the 
cylinder. Some simple tools are required which are generally 
available, with the exception of the trams, which may be readily 



HANDBOOK ON ENGINE KKING. 



229 



made for the purpose. Two trams are re(iuired, one of wliicli 
should be 6" or 7" long and the other about 24" or 30", as the 
condition may require. The smaller tram may be made of J" 
steel wire with the points turned over at right angles to the body, 
so as to project about 1". The points should be sharpened so 
that a hair line may be drawn by them. The larger tram should 
be made from rod of at least |" diameter and the points made in 
the same way as for the smaller tram. Oftentimes, the long tram 




Finding the Dead Center. 

is made with one leg longer than the other, on account of being 
handier to reach some stationary part, but this is a minor point, 
which has nothing to do with the principle to be described. The 
other tools required are a light hammer, a prick-j)unch, a pair of 
10" or 12" wing dividers and a hermaphrodite caliper, or a scrib- 
ing block. A piece of chalk will also be found convenient to 
facilitate scribing lines on the metal parts with the trams or 
dividers. 

Having the necessary tools, w^eare ready to begin oiDcrations, — 
you may start at either end of the stroke, as circumstances may 
favor. The fly-wheel is turned so that the crank stands at 
about the angle shown in the accompanying illustration, which 



230 HANDBOOK ON ENGINEERING. 

may, however, be approximated as the oi3erator may desire. The 
effort made, being to give sweep enough to the cross-head to 
allow accurate measurements and still not have such an excessive 
arc on the fly-wheel as to make its bisection difficult. 

A prick mark is made on the guides, or some convenient sta- 
tionary point, as at jB, and an arc struck on the cross-head with 
the small tram. At the same time, an arc is scribed on the rim 
of the fly-wheel at (r, using some convenient point for the lower 
point of the tram as at K. The fly-wheel is now turned until 
the crank passes the center and the cross-head travels back until 
the scribed line will coincide exactly with the point of the tram 
when held in the same position as in the first case. When this 
point has been reached, the wheel is stopped and a second arc is 
scribed on the fly-wheel rim at F with the tram J. The herma- 
phrodite caliper, or the scribing block, is now used to scribe a 
concentric line D E on the fly-wheel rim and the arc C F is 
bisected with the dividers. When the center TI has been accur- 
ately located, it should be carefully prick-marked. The scribing 
of the concentric line D E is a, refinement that is not strictly 
necessary if care be taken to locate the points of the dividers at 
the same distance from the outer perij^hery of the wheel in each 
instance when finding the center H. The marks left by the lathe 
tool will sometimes be plain enough for a guide. When the center 
II has been found, the fly-wheel is turned so that the point of the 
tram will fall into the prick-mark II when its lower end is in the 
stationary point K. When this condition is effected, the crank 
is exactly on the dead center and the position of the valve may 
be taken with confidence that its location at the dead center point 
is accurately found. The same procedure is followed to place the 
crank on the dead center at the opposite end of the stroke. 

The cut on page 231 is an elevation of Tandem Compound 
Engine, showing engine erected on brick foundation. It also 
shows a line through cylinders ; also a line over the shaft. 



HANDBOOK ON ENGINEERING. 



231 



232 HANDBOOK ON ENGINEERING. 

These lines are used in the erection of a new engine, or to Une 
up an old one, or with an engine that is out of line. The cut also 
shows how the foundation is made ; also how the anchor bolt 
is fastened. 

The cut on page 233 shows how to pipe a Twin Tandem 
Compound Condensing Engine. The plan shows two receivers, 
heaters, relief valves, gate valves, etc., and is so arranged 
that either side can be run independently of the other. It 
also shows how to line a pair of these engines up by following 
the lines and noting the distance between each line. An engineer 
would have no trouble in lining up a pair of these engines. 

HOW TO LINE AN ENGINE. 

The method followed when lining different types of engines, 
such as vertical, horizontal, portable, etc. :— 

The method followed in lining any piston engine is essentially 
the same in all cases, as far as determining when adjustments are 
needed. The method of making the adjustments after the char- 
acter and amount of them is determined, depends entirely on the 
construction of the engine, and will necessarily have to be deter- 
mined in each individual case. Lining an engine consists of ad- 
justing the guides so they shall be parallel to the bore of the 
cylinder, and in such a position that the center of the piston 
socket of the cross-head shall coincide with the axis of the cylin- 
der. Under these conditions only, can the piston and cross-head 
travel through the stroke freely, and without distorting any of the 
parts. After this adjustment has been made, the truth of the 
right-angle position of the shaft must be determined as being 
"out of square ;" this will make an engine run badly, and. is 
often the unsuspected cause of much trouble to engineers. We 
will assume that we have an engine with four-bar or locomotive 
guides, and that the connecting rod, cross-head, back cylinder 



HANDBOOK ON ENGINEERING. 



233 




234 



HANDBOOK ON ENGINEERING. 



head and piston have been removed. If the engine is of the 
horizontal type, the first step will properly be to ascertain if the 
engine is level on the foundation, and if not, proceed to make it 
so. After having leveled the engine, stretch a smooth linen 
line, as shown in Fig. 1, through the bore of the cylinder and 
the stuffing box, to a point beyond the shaft, where it should be 
attached to an iron rod driven into the floor. The other end is 
fastened to a cross-bar bolted across the face of the cylinder to 



S. FI3.Q. 




\ O cEj O I 



two of the studs, as shown in Fig. 4, or the bar may preferably 
be somewhat longer than one-half of the diameter of the cylinder, 
and with a saw cut for a short distance lengthwise at the inner 
end. In this case, it is held by only one of the cylinder studs 
and can be somewhat more easily adjusted. The line or cord is 
adjusted to approximately the proper position, and is drawn taut 
and fastened through the cross-bar by being tied to a short stick 
that is too long to pass through the hole. In this position it is 
held by the friction, and can be readily adjusted to the required 
position. An assistant is required to move the line in the direc- 
tions indicated, as the work proceeds, and then you are ready to 
center it in the cylinder. The only tool required for this purpose 
is a light pine stick of slightly less length than the radius of the 



HANDBOOK ON ENGINEERING. 235 

bore, and it should have an ordinary pin pushed into the head for 
a " feeler." Now adjust the line in the cylinder so that the head 
of the pin will just tick the line from four points of the counter- 
bore, which is always the part of the cylinder to work from, as it 
is not affected by the wear. The line should then be adjusted 
to the center of the other end of the cylinder, but not from the 
stuffing box, as this is likely to be out of center somewhat. 
Make the adjustment at this end from the counterbore, if pos- 
sible, the same as in the first instance, and then it will be neces- 
sary to try the position of the line in the back end of the cylinder, 
as the changes made at the other end will affect it slightly. After 
the line is truly centered, you are ready to adjust the guides. 
With some types of cross-heads, it is possible to use the cross- 
head for determining the proper location of the guides, but with 
the ordinary form, such as shown in Fig. 2, this cannot be done, 
but you will need a tool similar to that shown in Fig. 3, which 
consists simply of a piece of flat iron long enough to reach across 
the guides, and having a hole drilled and tapped in the center for 
the thumb-screw. This thumb-screw is adjusted so that its point 
is the same distance from the lower side of the bar, as the lower 
face of the wings of the cross-head are from the center of the 
piston socket. To find this distance, lay a straight edge across 
the end of the cross-head and draw the line A B, and then, hav- 
ing found the center of the hole, the measurement may be accur- 
ately taken. The lower guides are now adjusted by the tool, so 
that the point of the screw will tick the line throughout the 
length, and then the top guides are put in position with the cross- 
head in place and adjusted for a proper working fit. 

Before removing the line from the cylinder, however, the shaft 
should be tested for the truth of its right-angle position, which 
msij be done by calipering between the crank disc and the line at 
the points H and I. If the distances are equal, the shaft is 
square with the bore of the cylinder, providing, of course, that 



236 HANDBOOK ON ENGINEERING. 

the disc is faced true with the shaft. If there is any doubt as to 
its accuracy, turn the shaft as nearly half way around as the 
crank-pin will admit without disturbing the line. Then caliper 
the distance of a point on the disc that will not be far removed 
from the first position, thus reducing the chance for error. If 
the shaft shows " out," move the outward bearing until the meas- 
urements show equal in both positions. The horizontal truth of 
the shaft can be found by laying a level on it, and if "out," 
raise or lower the out-board bearing until the level shows fair. 
Work of this kind requires skill and patience and belongs j:)rop- 
erly to the sphere of the chief engineer. It requires a delicacy of 
touch and an appreciation of what is meant by close measurement 
that can come only throug;h experience. In centering the line, 
one should be able to detect when it is as little as y qVo ^^ ^^ iuch 
out of center. A piece of ordinary tissue paper is about .00125 
inch thick. A man should be able, therefore, to adjust a line so 
accurately that if the " feeler," with one or more pieces of the 
paper under it, just clips the line, it will miss the line when one 
thickness is removed. While it may not always be necessary to 
work as closely as this, a person cannot expect to line up engines 
successfully until he has a full knowledge of what this degree of 
accuracy means. 



HANDBOOK ON ENGINEERING. 237 



CHAPTER XII. 
THE STEAM ENGINE, — Continued. 

Work consists of the sustained exertion of force through space. 
The unit of work, the foot-pound, is a force of one pound exerted 
through one foot space. The work done in lifting one pound ten 
feet, or ten jwunds one foot, is ten-foot pounds. 

Power is the rate of work, or the number of foot-pounds ex- 
erted in a unit of time. The unit of power is the horse-power, 
and equals 33,000 foot-pounds exerted in a minute, or 550 foot- 
pounds exerted in a second, or 1,980,000 foot-pounds exerted in 
an hour. An engine developing fifty-horse power, exerts 27,500 
foot-pounds per second, 1,650,000 foot-pounds in a minute. It 
could raise (friction neglected) 41,250 pounds forty feet in one 
minute. 

A belt running over a pulley at 4,000 feet per minute, pulling 

with a force of 240 pounds (fair load for a 4-inch belt) will 

transmit 

240x4,000 

— oo QQQ — equal thirty horse-power (nearly). 

If moving at 1,100 feet per minute, the result would be 

240x1,100 

— oo QOf) — equal eight horse-power. 

A gfear-wheel, the cogs of which transmit a pressure of 1,800 
pounds (fair load for li" pitch 6" face) to the cogs of its mate, 
the periphery velocity of the wheels being ten feet per second, 
transmits 

1,800 X 10 



550 



equal thiiliy-three horsepower nearly. 



238 HANDBOOK ON ENGINEERING. 

If speed was 360 feet per minute, it would transmit 

1,800x360 

— Q„ ^^^ — equal twenty horse-power nearly. 

The hofse-powei" developed by a steam engine consists of two 
primary factors. Piston Speed and Total Average Pressure of 
steam upon the piston. 

Piston speed depends upon the stroke of engine and the num- 
ber of revolutions per minute. An engine with stroke of twelve 
inches, making 300 revolutions per minute, has a piston speed of 

2 X 12 X 300 

r-^ equal 600 feet per minute. 

Piston speed of an engine with 24" stroke at 150 revolutions 

per minute : 

2x24x150 

r^ equal 600 feet per minute. 

Total averagfe pressure depends on area of pist07i and mean 
effective pressure per square inch exerted on piston throughout 
stroke. The mean effective pressure (M. E. P.) in any case can 
only be accurately obtained by means of the steam engine indi- 
cator, and depends upon the load engine is carrying. 



GENERAL PROPORTIONS. 

Diameter of steam pipes : 

Slide-valve engine, J diameter of piston. 
Automatic high-speed engines, i diameter of piston. 
Corliss engine, y3_. diameter of piston. 

Diameter of exhaust pipes : 

Slide-valve engine, i diameter of piston. 
Automatic high-speed engine, | diameter of piston. 
Corliss engine, J to | diameter of piston. 



HANDBOOK ON ENGINEERING. 239 

Displacement of piston 

Clearance spaces: in one stroke. 

Slide-valve engine 0.06 to 0.08 

Automatic high-speed engine, single valve . 0.08 to 0.15 

Automatic high-speed engine, double valve . 0.03 to 0.05 
Automatic cut-off engine, Corliss type, long 

stroke 0.02 to 0.04 

Weigfhts of engfines per rated horse-power : 

Slide-valve engine 125 to 135 lbs. 

Automatic high-speed engine 90 to 120 lbs. 

Corliss engine . 220 to 250 lbs. 

Fly-wheels, weigfht per rated horse-power : 

Slide-valve engine 33 lbs. 

Automatic high-speed engine 25 to 33 lbs. 

(According to size and speed.) 
Corliss engine 80 to 120 lbs. 

(According to size and speed.) 

RULES FOR FLY=WHEEL V/EIQHTS, SINGLE CYLINDER 
ENGINES. 

Let d = diameter of cylinder in inches. 

S = stroke of cylinder in inches. 

D = diameter of fly-wheel in feet. 

a = revolutions pev minute. 

W = weight of fly-wheel in pounds. 

. cZ2 S 
For slide-valve engines, ordinary duty . 1^=350,000 ^^ 732 

d^ S 
For slide-valve engines, electric lighting. W= 700,000 y^riTi 

d'^ S 
For automatic high-speed engines . . W= 1,000,000 ^^ P2 



240 



HANDBOOK ON ENGINEERING. 



For Corliss engines, ordinary duty . . W= 700,000 
For Corliss engines, electric lighting .. W = 1,000,000 



d^ S 







The Russell Engine.^ 

SETTING THE VALVE ON A RUSSELL ENGINE, SINGLE VALVE 
TYPE. THE SAflE PRINCIPLE LAID DOWN IN THE SET= 
TING OF THE COHMON SLIDE VALVE MUST BE ADHERED 
TO. 

The style of valve is shown in cut. Fig. 1. It is, to some 
extent, a moving steam chest with the steam all within itself , 
admitting only enough steam into the chest to keep the valve to 
its seat, against the maximum tendency to leave it. This pres- 
sure in the chest is found with the valve as at present propor- 
tioned, to be about 45 per cent of that contained within the 
valve. The cut shows the valve and section of cylinder so 
plainly as to render any detailed explanation of same almost 
unnecessary. 



HANDBOOK ON ENGINEERING. 



241 



The eccentric operating the valve is under control of the gover- 
nor, as shown in cut Fig. 2, which regulates the speed of the 
engine by sliding the eccentric across the shaft, either forward or 
backward, as the weights change their position, thereby cutting • 
the steam off earlier or later in the stroke, as the governor, or 
more properly, the weights adjust themselves to the load. 

When the eccentric is moved across the shaft in a direction 
that reduces its eccentricity, the steam is cut off earlier in the 




(Fia 1) 



stroke; when the eccentric is moved in the opposite direction, 
the steam is cut off later in the stroke. The extreme range of 
this cut-off is from to J of the engine's stroke, and this 
whole range of adjustment is under complete control of the 
governor. 

Xo preserve a certain determined speed with the smallest pos- 
sible variation, as changes occur in the load or pressure, is the 
function of the governor. The cut-off must always be propor- 
tioned to the load. When the engine is running empty, the steam 
is cut off at the beginning of the stroke and the governor weights 
are at their extreme outer position. With a heavy load, steam 
follows further and the weiglits are nearer their inner position . Be- 

16 



242 . HANDBOOK ON ENGINEERING. 

tween these two limits, any number of positions of the weights, and 
corresponding angular positions of the eccentric, may be had ; and 




Fig. 2. 

as the steam is thus adapted to the load in each position, it follows 
that a slight increase or decrease in speed must make a change in 
the cut-off and bring the engine again to standard speed. 



HANDBOOK ON ENGINEERING. 243 

In setting the valves it is necessary to mark the ports in the 
valve face at the outer edge of the steam chest, and also to mark 
on the back of the valve the ports in its face, so that it may be 
adjusted after being placed in the chest, in which ^^osition it pre- 
sents a blank surface that, without these marks, would afford no 
means for knowing its position. 

In placing the valve in the chest, see that it fits perfectly 
against the seat and that the bottom bearing, on which the valve 
rides, is at right angles to the valve seat, and in such a condition 
that the valve will not be tipped away from its seat, but rather 
against it. This latter condition will be insured by easing off 
the bottom strip at the inner corner, so that the valve would 
bear hardest at the outer edge. The hinge nut, into which the 
valve stem is screwed, as well as its trunnion bearings, should 
fit so that the valve lays closely to its seat, rather than be held 
away from it. 

Having extended the marks of the ports as well in the valve 
seats as in the valve itself, to the outside, it now becomes neces- 
sary to get the center of the travel of the eccentric and connect 
the valve and rod, so that the valve will travel equally on either 
side of this center. The throw of the eccentric leads the crank in 
the direction the engine runs, and with the eccentric properly 
located, as it cannot help being, because it is attached to the 
governor and the governor is keyed to the shaft, the lead will 
remain the same with the governor weights in their outer as well 
as in their inner positions. 

Tliese valves are usually marked with the engine on the center 
at either end, marks corresponding with the admission edges of 
valve and seat. The hinge nut connection makes it convenient to 
examine these valves without disconnecting or disturbing any 
adjustments made. The valve rod has right and left-hand threads 
for adjustment, and final adjustment can be made without taking 
off the steam chest cover. 



244 HANDBOOK ON ENGINEERING. 

Of course, the proper way to make the final adjustment is by 
the aid of an indicator, but if the indicator is not at hand the 
engineer can, by the use of the right and left-hand threads, adjust 
the valve to a nicety. 

While the engine is running slowly, leave the holes for the in- 
dicator connection open and notice the sound of the steam escap- 
ing through these openings. Then, with a wrench on the valve 
stem, the sound can be made even at both ends and the valve 
will be surprisingly close to the proper point of adjustment. In 
fact, a good ear can adjust in this way so closely that a subse- 
quent indicator test will fail to find very much wrong. 




'■#^ 



Four Valve Type. 

To set the valves on a four-valve Russell Automatic Engine, 
in which admission and cut-off is controlled by two separate 
valves. Fig. 3, and where, as in the four-valve Russell Automatic 
Engine, the exhaust is controlled by a separate arrangement of 
valves. Fig. 4. This arrangement has many advantages over the 
single-valve type, as the admission, release and compression all 



HANDBOOK ON P]NGTNEERTNG. 



245 



remain constant for whatever cat-off ; the economy of the engine 
is not nearly so dependent on a certain point of cut-off as is the 
single-valve type. 




Fig. 3. 

In the engine under consideration , the release and compression 
can be very readily and nicely adjusted by simply loosening the 
nut, clamping the arm, shown in cut, Fig. 5, to the valve stem ; 
then by putting the wrench on the square end of the valve stem, 




Fig. 4. 

shown in Fig. 6, the valve can be turned to any amount of com- 
pression, as shown by the pointer and graduated index. 

Fig* 7 shows a section through the valve and cylinder, reveal- 
ing a portion of the piston and showing the point of compression 
at its beginning. Piston being within three inches of the end oi 



246 



HANDBOOK ON ENGINEERING. 




HANDBOOK ON ENGINEERING. 247 

its travel, the exhaust port has just been closed, as denoted by 
the direction of motion of exhaust valve, shown by arrow. 

In setting" the valves of this engine, put in main valve ; find 
its point of mid-travel by placing it alternately at points of 
opening to cylinder, marking face of seat lightly along the 
admission edge of valve at the other end, and then moving valve 
until the distances between these marks and the admission edges 
of valve are equal. 

Mark this position with a chisel. Leaving main valve at mid- 
travel, put in cut-off valve and move it along until it shows equal 
port openings at each end with main valve. Mark this position 
with a chisel. Put on main and cut-off valve stems and long 
and short exhaust connections, adjusting their lengths so that 
the rocker arms will stand plumb when main and cut-off valves 
are at mid-position and wrist plate is plumb. 

To plumb wrist plate, mark distance between the center of 
the exhaust valve stems and the small pins in wrist plate, to which 
the exhaust valve stems are connected equally. Put on con- 
necting rod. 

Next^ put on main eccentric so its throw will lead that of the 
crank in the direction the engine is to run. The shaft and eccen- 
tric being key-seated, the eccentric cannot be placed wrong if 
this point is observed ; namely, that the throw, or heavy side of 
the eccentric, will lead that of the crank in the direction the 
engine is to run. The eccentric being in halves, it can be taken 
off and turned around so that the face that is next to the cut-off 
eccentric will be next to the pillow block, and this operation 
reverses the motion of the engine. Figs. 8 and 9. 

Put on main eccentric rod, and adjust its length by nuts at 
straps until main valve shows equal opening at the same end at 
which piston or cross-head is, with engine on center. Attach 
cut-off eccentric and rod. Turn the eccentric by hand on shaft, 
and adjust length of rod as before until cut-off valve travels 



248 



HANDBOOK ON ENGINEERING, 



equally on each side of its middle position, as found previously. 
Put governor together, so weights will follow or drag behind the 




trunnions in arms of governor wheel, to which they are attached 
when engine is running. 



HANDBOOK ON ENGINEERING. 



249 



Block weights one-half way out. Turn engine over in the 
direction it is to run until the cross-head has traveled one-eighth 
to one-sixth of its whole stroke. With governor wheel loose on 
the shaft, turn it in the direction engine is to run until cut-off 
valve closes ports in the main valve from which the cross-head is 
traveling. Fasten governor wheel to shaft. 



f OFCYUINOCR 




' $ OF EXHAUST WLVe COMN.ROD 

Fig. 10. 



'^o,%^A,,, 



Now try the cut-off for both ends, adjusting t-he cut-off valve 
rod by the union nut or swivel, until it cuts off at equal points 
in the stroke. 

The compression is shown by the index upon the exhaust 
valve arms, which may be verified or corrected if the index has 
become disarranged by markings on the back of ends of exhaust 
valves and chest. 




" ^((OPCXHAU8TVAI.VCCONN.R00 / 

Fig. 11. 



^^tttL^^ 



The two diagrams, cuts. Figs. 10 and 11, show the different 
positions of the exhaust valves, with relation to the different 
positions of crank ; and they also show the arrangement of motion 
of these exhaust valves, as transmitted through the double bell 
crank or exhaust valve rocker, to which they are connected. 



250 



HANDBOOK ON ENGINEERING, 




HANDBOOK ON ENGINEERING. 251 

This motion is such that during the admission of steam when the 
highest pressure is on the exhaust valve, its speed is at its mini- 
mum, and at the moment of release, when the pressure is 
reduced to its lowest tension, its travel is at its maximum. This 
serves the double purpose of reducing the wear on the valves and 
making a comparatively sharp corner on the indicator card at the 
point of release. 

DIRECTIONS FOR SETTING UP, ADJUSTING AND RUNNING 
THE IMPROVED CORLISS STEAM ENGINE. 

Location of foundation* — The foundation must be at right 
angles with main line shaft. If main line shaft is not already in 
position, then foundation must be set by two points, located and 
connected with a line parallel with the buildings, and at right 
angles to an imaginary line through center of cylinder. 

Foundation plans should show all center lines. If a templet 
is furnished to locate the foundation accurately for the mason, the 
center line of engine cylinder and guides and right angle for 
crank center are drawn thereon. 

Cap stones* — Examine carefully the lap faces of cap stones 
and, if necessary, have them trimmed off by cutter or mason, so 
that each is true and level, and in exactly the plane shown in 
formation plan. 

Cylinders and frame. — Put engine cylinder and frame in 
position and bolt them together. 

Lining: off crank shaft and out-end bearing* — Stretch a 
line at right angles to main center line, through main bearing to 
represent center line of crank shaft. See that this line is exactly 
in the center and level. By this line place out-end bearing square 
and true. Put crank shaft in its bearings after bottom box has 
been placed in main bearings. Insert quarter boxes and 
adjusting wedges into main bearing and put cap on. 

To ascertain that shaft is at exact right angles to main center 



252 HANDBOOK ON ENGINEERING. 

« 

line, turn engine shaft until tlie crank-pin comes nearly to the main 
center line, then with a pair of calipers, or rule, measure from 
shoulder of crank-pin to line, and after noting this distance, turn 
the crank back towards opposite center until pin is in same 
relative position to line, and measure again. If both measurements 
do not correspond, out-end bearing must be moved either way as 
required, until measurements show equal. Then take up slack 
around shaft in main bearing, being careful not to force the 
adjusting wedge too tight. 

Fly-wheels* — The fly-wheel is next placed on shaft and firmly 
keyed in position. 

Placingf valve gear* — Steam and exhaust valve covers or bon- 
nets on valve gear side are next bolted to place, taking care that 
no dirt or foreign substance gets between the surface underneath 
the covers. 

Valve stems are inserted from opposite or front of cylinder and 
the valves put in after them, the F head of valve stem entering 
slot in valve. Couple up all valve gear parts, i. e., disc plate, 
valve-stem cranks, valve-connecting rods, dash pots and dash-pot 
rods, valve-rod rocker, eccentric and straps on crank-shaft, first 
and second eccentric rods. The dash pots should be thoroughly 
cleaned and oiled before putting in place. 

I Valve gear adjustment. — The valves are well 

Fi^'f. marked to their respective places in the cylinder. 

All the valve connections are screwed up tight 
to proper length (after adjustment and setting 
of valves in shape). The dash pot connecting 
rods require adjustment after dash pots are in 
place. (In the present style of engines the posi- 
tion of dash pots is unalterably fixed by a finished 
seat for each in the feet of cylinder.) Move disc 
plate (Fig. 1) until line /marked on same meets 
line marked on fixed disc bracket, then adjust 




HANDBOOK ON ENGINEERING. 



253 




the dasli pot so that the hook of the lever connecting rod to 
steam valve stem engages the catch block free and easy ; repeat 
this with the other steam valve connecting rod. 

Note. — The 1 and 2 on disc plate represents travel of same. 
The first eccentric rod will require no adjustment if placed thus: 

(see Fig. 2) it 
being so marked 
on every engine, 
and the measure- 
Bcrr«cr^»cte^^^''^t^ from nut 
to mark being al- 
ways two inches. 
Secure the eccen- 
tric to the shaft as it is marked, always ahead of the crank, 
whichever way the engine is required to run. 

Gover non — Bolt the governor stand to its place on engine 
frame, first removing any grit or dirt upon surfaces which come 
together. Connect the cut-off rods to cut-off cams, also the gov- 
ernor rods and fixtures. The cut-off rods are already adjusted 
to proper length before shipment from the shop and screwed up 
tight. If loosened by accident, they should be set JFi^-S. 
thus : Set the governor in the top notch of the collar 
(see Fig. 3) ; unhook second eccentric rod from disc 
plate, and with hand lever (which insert in disc plate 
for the purpose) move valve gear to one end of 
travel (as indicated by lines i and 2 on disc plate and 
center line on fixed disc bracket (see Fig. 1) and 
adjust the rods so that steel trip toe on cut-off can 
just touch the claw without unhitching same. Re- 
verse disc plate and repeat this on the other end. i 

Safety collan — The safety collar on governor (^AFig. 3) is 
provided with a spring which turns said collar. This collar is 
properly spaced so that the deep notch takes place of shallow 




254 



HANDBOOK ON ENGINEERING. 



one, and should governor belt break, the governor would drop 
so low that the adjustable toe on cut-off prevents claw from 
engaging catch block, thus stopping the engine, as no steam will 
be admitted to the cylinder. 




Fig. 4. 



Setting valves* — If the length of valve rods should have 
changed by accident, place valve disc on center (0 to 0, Fig.l) ; 
remove back valve chamber covers where edge of ports and valves 
and the parts are marked plainly by chiseled lines, and set the 
valves as per marks. 

Adjust the length of eccentric rod so that the valve disc swings 
equalboth ways from the center line on hub of disc (see Fig. 1). 
Place the valve disc in the center (lines and 0, Fig. 1) and set 
the valve as shown above, the admission or steam valves to have 
-f^ inch lap, the exhaust port valves edge to edge. 

Set the crank on dead center. (To get engine on center see 
page 228.) Turn the eccentric ahead of the crank pin in the direc- 
tion the engine is to run until the valve shows J^ inch opening, 
then secure the eccentric. If any difference of opening is detected , 
it can be adjusted by the nuts on eccentric rod, moving the rod 
in or out as the case may require. 

Piston* — Before placing the piston in cylinder, remove the 



HANDBOOK ON ENGINEERING. 255 

exhaust valves from their seats and insert starting bar in wrist 
plate. After lifting hook up off pins place wrist plate in central 
position (as shown by lines and 0, Fig. 1) and admit a small 
amount of steam through stop valves. Then b}^ working the wrist- 
plate back and forth with starting bar, the dirt and grit will be 
entirely removed from the interna,l surface of cylinder and steam 
passages. 

CONDENSERS. 

When steam expands in the cylinder of a steam engine, its 
pressure gradually reduces and ultimately becomes so small that 
it cannot profitably be used for driving the piston. At this stage, 
a time has arrived when the attenuated vapor should be disposed 
of by some method, so as not to exert any back pressure or 
resistance to the return of the piston. If there were no atmos- 
pheric pressure, exhausting into the open air would effect the 
desired object. But, as there is in reality a pressure of about 
14.7 pounds per square inch, due to the weight of the super- 
incumbent atmosphere, it follows that steam in a non-condensing 
engine cannot economically be expanded below this pressure, and 
mast eventually be exhausted against the atmosphere, which 
exerts a back pressure to that extent. 

It is evident that if this back pressure be removed, the engine 
will not only be aided by the exhausting side of the piston being 
relieved of a resistance of 14.7 pounds per square inch, but 
moreover, as the exhaust or release of the steam from the engine 
cylinder will be against no pressure, the steam can be expanded 
in the cylinder quite, or nearly, to absolute of pressure, and 
thus its full expansive power can be obtained. 

Contact^ in a closed vessel, with a spray of cold water, or with 
one side of a series of tubes, on the other side of which cold 
water is circulating, deprives the steam of nearly all its latent 
heat, and condenses it. In either ease the act of condensation is 



256 HANDBOOK ON ENGINEERING. 

almost iostantaneous. A change of state occurs and the vapor 
steam is reduced to water. As this water of condensation only 
occupies about one sixteen-hundredths of the space filled by 
the steam from which it is formed, it follows that the remainder 
of the space is void or vacant, and no pressure exists. Now, the 
expanded steam from the engine is conducted into this empty or 
vacuous space, and, as it meets with no resistance, the very limit 
of its usefulness is reached. 

The vessel in which this condensation of steam takes place is 
the condensing chamber. The cold water that produces the con- 
densation is the injection water ; and the heated water, on leaving 
the condenser, is the discharge water. To make the action of the 
condensing apparatus continuous, the flow of the injection water 
and the removal of the discharge water, including the water from 
the liquefaction of the steam, must likewise be continuous. 

The vacuum in the condenser is not quite perfect, because the 
cold injection water is heated by the steam and emits a vapor of 
a tension due to the temperature. When the temperature is 110 
degrees Fahr. , the tension or pressure of the vapor will be 
represented by about 4" of mercury ; that is, when the mercury in 
the ordinary barometer stands at 30", a barometer with the space 
above the mercury communicating with the condenser, will stand 
at about 26". The imperfection of vacuum is not wholly traceable 
to the vapor in the condenser, but also to the presence of air, a 
small quantity of which enters with the injection water and with 
the steam ; the larger part, however, comes through air leaks and 
faultly connections and badly packed stuffing boxes. The air 
would gradually accumulate until it destroyed the vacuum, if 
provision were not made to constantly withdraw it, together with 
the heated water by means of a pump. 

The amount of water required to thoroughly condense the 
steam from an engine is dependent upon two conditions : the total 
heat and volume of the steam, and the temperature of the injection 



HANDBOOK ON ENGINEERING. 257 

water. The former represents the work to be done, and the latter 
the value of the water by whose cooling agency the work of con- 
densation of the steam is to be accomplished. Generally stated, 
with 26" vacuum, the injection water at ordinary temperature, not 
exceeding 70° Fahr. , from 20 to 30 times the quantity of water 
evaporated in the boilers will be required for the complete 
liquefaction of the exhaust steam. The efficiency of the injection 
water decreases very rapidly as its temperature increases, and at 
80° and 90° Fahr., very much larger quantities are to be employed. 
Under the conditions of common temperature of water and a 
vacuum of 26" of mercury, the injection water necessary per 
H. P. developed by the engine, will be from IJ gallons per minute 
when the steam admission is for one-fourth of the stroke, up to 
two gallons per minute, when the steam is carried three-fourths of 
the stroke of the engine. 

CORLISS ENGINE REGULATION. 

The question of why an ordinary Corliss Engine will not cut 
off later than about half stroke, is often asked by engineers, 
although the reason is simple. 

When the engine is on a center, the eccentric must be a little 
ahead of the vertical position in order to give the valves an open- 
ing at the correct time. By the time the piston has reached about 
half stroke, therefore, the eccentric will have reached its extreme 
travel one way, and the valve lever will begin to move back in the 
opposite direction. Now the nature of the mechanism is such 
that the valve can be tripped only when the valve lever is moving 
in a direction which will bring the trip arrangement or catch, 
against the knock-off lever. Just as soon as it begins to move 
back away from the knock-off lever, which it does at about half 
stroke, owing to the motion of the eccentric, cut-off cannot be 
effected by the action of the governor. 

17 



258 



HANDBOOK ON ENGINEEKING. 




HANDBOOK ON ENGINEERING. 259 

THE PORTER=ALLEN STEAM ENGINE, MADE BY THE 
SOUTHWARK FOUNDRY & flACHINE CO. 

This engine claims the distinction of being the original and 
most perfect type of the high-speed steam engine. In truth, 
however, it should not be termed a high-speed engine. Relatively, 
indeed, to those speeds to which it has hitherto been found neces- 
sary to limit the motion of engines, its speed is high ; but consid- 
ered absolutely, and as it appears to all persons accustomed to it, 
this engine is ordinarily run at what is undoubtedly the natural, 
and on all accounts, the desirable speed at which a properly 
designed and constructed steam engine ought to be run, for ordi- 
nary purposes ; while this is much below the speed of which it is 
capable, and at which it is run with entire success, in cases where 
such speeds are required. This engine is presented as one which, 
distinguished by a system of valves and valve movements per- 
fectly adapted to improved rotative speed, has also been designed 
upon sound principles, and is made in the most excellent manner ; 
so that, without the least drawback, all the advantages of this 
speed may be realized by the use of it. A description of this 
engine naturally commences with the valve gear and valves. 

Its central feature is a link actuated by a single eccentric, 
from which separate and independent movements are given to the' 
admission and the exhaust valves. 

Attention is first invited to 

The position of the eccentric* — The eccentric is placed on the 
shaft in the same position with the crank, and cannot be altered 
from this position. The lead of the valves is adjusted by other 
means. The first requirement of this system is, that the crank 
and the eccentric shall have coincident movements, and so shall 
arrive on their dead points, or lines of centers, simultaneously. 

To insure the permanence of the eccentric in its correct posi- 
tion, and also for compactness, and as a superior mechanical con- 



260 



HANDBOOK ON ENGINEERING. 



struction, it is formed in one piece with the shaft, and its low 
side is brought down to the surface of it, as shown in Fig. 1. 

The link, — The construction of the link is also shown in 
Fig. 1. It is of the form known as stationary link, and con- 
sists of a curved arm, partly slotted, formed in one piece with the 
eccentric strap, and pivoted at its middle point on trunnions, which 




Fig. 1. 

vibrate in an arc whose chord is equal to the throw of the eccen- 
tric, about a sustaining pin secured rigidly to the bed. The 
radius of the link is equal to the length of the first rod, by which 
its motion is communicated to the admission valves. 

In the slot is fitted a block from which the admission valves 
receive their motion. This block is moved by the action of the 
governor, which thus varies the point of cut-off. If the center 
of the block is brought to the center of the trunnions, the port is 
not opened at all, except by the lead given to the valves, and this 



HANDBOOK ON ENGINEERING. 261 

Opening is closed before the piston has advanced a sensible 
amount. If, on the other hand, the block is brought to the end 
of the slot, as here represented, the steam is not cut off until the 
piston has reached about six-tenths of the stroke, which is the 
limit of the admission. 

The exhaust valves are driven from a fixed point on the link, 
and have, of course, an invariable motion. The movements of 
the link at this point are admirabl}^ suited to this function, caus- 
ing the steam, wherever it may have been cut off b}^ the admis- 
sion valves, to be held until near the termination of the stroke, 
when it receives a free and ample release, and is confined again 
near the end of the stroke by the closing of the exhaust valves at 
a point which provides the compression required to arrest the 
motion of the reciprocating parts, and at the same time, fill the 
end clearance of the cylinder with the compressed steam. 

The peculiar motion of the link is given to it by a combination 
of the horizontal and the vertical throws of the eccentric. The 
horizontal throw alone only moves the link from one to the other 
of the lead lines, which motion only draws off the lap of the 
valves: The opening movement is produced by the tipping of the 
link alternately in the opposite directions beyond the lead lines, 
and these tipping motions are given by the vertical throws of the 
eccentric. Its upward tkrow tips the link in the direction from 
the shaft and opens the port at the further end of the cylinder ; 
and its downward throw tips the link towards the shaft, and 
opens the port at the crank end of the cylinder. At the same 
time, its horizontal throw is drawing the valve back, and when in 
this return movement, that point in the link at which the block 
stands, crosses the head-line, the steam is cut off. 

This link possesses a distingfuishingf excellence^ which will 
now he described. — The angular vibration of the connecting rod 
causes a considerable difference in the motion of the piston in 
the opposite ends of the cylinder, retarding it in the end 



22bZ HANDBOOK ON ENGINEERING. 

nearest to the crank, and accelerating it at the end farthest from 
it. When the length of the connecting rod equals six cranks, as 
is usually the case, this difference in velocity averages 20 per 
cent, and at the commencement and termination of the strokes, 
reaches the great amount of forty per cent. 

The driven arm of the link is of such length that its angular 
vibration coincides in degree, as well as in time, with those of 
the connecting rod ; and so the trunnions of the link receive a 
motion coincident with that of the piston, and the link gives to 
the valves, in opening and closing their ports, different velocities, 
accelerated at one end of the cylinder and retarded at the 
other, corresponding to the difference in the velocity of the 
piston. 

Difference of lead* — The application of this gear to the 
engine under an adjustment provides for a slight difference in 
lead at either end of the stroke, and the amount of this dissimi- 
larity is in the direct ratio as the variation of the piston velocities 
at the end of the stroke. 

The manner in which the link imparts to the exhaust 
valves their movements* — The exhaust valves open and close 
their ports in such manner that the opening is made while the 
valve is moving swiftly, and one-half of the opening movement 
has been accomplished when the piston arrives at the end of its 
stroke. The valves are so constructed that this portion of the 
movement opens the whole area of the port, which does not begin 
to be contracted again until the center line of the link has re- 
crossed the lead lines on its return. The speed of the piston is 
then also diminishing, and the exhaust is not throttled at all 
until the port is just about to be closed. 

The differential valve movement* — A wrist motion is intro- 
duced into the connection of the admission valves. 

In this movement^ an arm which is connected by a rod with 
the block in the link, communicates through a rock shaft, motion 



HANDBOOK ON ENGINEERING. 263 

to the two other arms, causing them to vibrate iu the same verti- 
cal plane in which the valves move. Each of these arms alter- 
nately rises nearly to the vertical position, while the other, at the 
same time, descends to and beyond its dead point. 

Each by a separate connection, imparts motion to one of the 
dmission valves, and at the top of its vibration causes it to open- 
and close its port swiftly and then, descending to its idle arc, 
reduces the motion of the valve to an interval practically of rest. 

These movements can be followed in the cut where the upper 
arm is about to move in its arc to the left, and thus, through the 
lower connections, to open the port at the further end of the 
cylinder, while the lower arm will be scarcely moving in its valves 
at all. In this manner, the width of opening is largely in- 
creased, chiefly by a difference in tiie length of the levers, while, 
at the same time, fully one-half of the lap, or the useless motion 
of each valve after it has covered its port, is got rid of, so that 
smaller valves and narrower seats are employed, and notwith- 
standing the greater opening movement, the total motion of the 
valves is very much reduced. 

THE ADJUSTABLE PRESSURE PLATES. 

Description of these plates* — The construction of these pres- 
sure plates and the method of adjusting them are fully represented 
in the sections of the cylinder. Figs. 2 and o. 

On the lower side of the horizontal section, Fig. 2, both 
admission valves are shown, working between their opposite 
parallel seats, one of which is formed on the cylinder, and the 
other on the pressure j^lates, the latter having cavities opposite 
the ports. 

The valve at the further end of the cylindei is at the 
extremity of its lap, while the one at the crank end has com- 
menced to open the four passages for admission of the steam. 



2(34 



HANDBOOK ON ENGINEERING. 



The vertical cross-section, Fig. o, passes through the middle 
of one i^ressure plate and shows its form and the means 
employed for its adjustment. It is made hollow and most of 




Fig., 2. 



the steam supplied to two of the openings passes through it. 
It is arched to resist the pressure of the steam without deflec- 
tion. It rests on two inclined supports, one above and the 
other below the valve. These inchnes are steep, so that the 
plate will be sure to move freely down them under the steam 
pressure, and also that it may be closed up to the valve with 
only a small vertical movement. It is prevented from moving 
down these inclines by a screw, passing through the bottom 
of the chest, the point of which, as also the plug against which 
it bears, is of hardened steel. 

The pressure plate is held in its correct position by projections 
in the chest, on one side, and tongues projecting from the cover 
on the other, which bear against it near each end, as shown. 



HANDBOOK ON ENGINEERING. 



265 



Between these guides, it is capable of motion up and down its 
inclined supports, and also directly back and forth between the 
valve and the cover. 

The pressure of steam is always on this plate, and tends to 
force it down the incline to rest on the valve. By means of 
the screw it is forced against the steam pressure, up the in- 
clines and away from the valve. This adjustment is capable of 
great precision, so that the valve works with entire freedom 
between its opposite seats, and still is steam-tight. 

How these plates act as relief valves* — Whenever the pres- 
sure in the cylinder exceeds that in the chest, the admission 




Fig. 3. 



pressure plate is instantly moved back to contact with the cover, 
thus affording an ample passage for the discharge of water 
before it can exert a dangerous strain. This plate is superior 



266 



HANDBOOK ON ENGINEERING. 



in this action to any of the ordinaiy forms of relief valve, both 
in the area opened, and also in being self -adjusted to the pressure, 
and opening fully the instant that is exceeded. 

How to keep the admission valves tight* — These valves, 
though moving in complete equilibrium, are liable to slight wear. 




IQ] fftl a. rm 




This should be taken up as it appears, by letting down the 
pressure plates. The construction of these plates and the method 
of adjusting them, are shown in the accompanying sections, made 
through the steam chest at one end of the cylinder. Of these, 
Figs. 1 and 2 are horizontal sections, showing the four-opening of 



HANDBOOK ON ENGINEERING. 



267 



the valve — first, when commencing to open, with arrows indicating 
the course of the steam ; and, second, at the extreme point of its 
lap; while Figs. 3 and 4 are vertical sections, showing the 




pressure plate — first, when by turning the bolt d forward it is 
forced up the inclines and away from the valve, producing a leak ; 
and second, when it is let down to its proper working position. 
A is the port, B the valve, and C the pressure plate. The latter 




is made with a trussed-back and so cannot be deflected by the 
steam pressure. Through the passage thus formed, the steam 
reaches two of the openings. 



268 HANDBOOK ON ENGINEERING. 

The pressure plate rests on two iucliiied supports, c, c, and 
the pressure of the steam forces it down these inclines as far 
as the bolt d underneath will allow. This bolt holds the plate 
just off from the valve, so that the latter moves freely, 
and is still steam tight. Whenever leakage appears, a minute 
turning of this bolt backwards lets the pressure plate down and 
closes it. 

Provision is made for readily detecting the least leakage, as 
follo^^s : When the engine is warmed up in its normal working 
condition, open the indicator cocks, or in the absence of these, 
remove the plugs from the top of the cylinder, unhook the link 
rod, and set the valves by the starting bar so that both ports are 
covered, and turn on the steam. If the valve leaks at the end of 
the cylinder, which is not then open to the atmosphere or the 
condenser, the steam will blow out at the opening provided, having 
no other outlet. Then let down its pressure plate by backing the 
bolt very carefully till the leak disappears. The valve should 
still move freely when the leak has disappeared, and the pressure 
plate must not be let down any closer than is necessary for this 
purpose. 

Leakage at the opposite end of the cylinder will not generally 
be seen, the steam escaping freely by the open exhaust. To test 
its valve in the same manner, the engine must be turned on to the 
opposite stroke. These examinations should be made from time 
to time. 

In the small engines which have no starting bar, the valve rod 
can be disconnected and moved by hand to test this point. 

An engine should never be started till it is warmed up. The 
valves warm quicker than the supports on which the pressure 
plates rest, and are tight between their seats by expansion, until 
the temperatures have become nearly equalized. Provision for 
detecting and stopping any leak of steam is the crowning 
excellence of this valve. 



HANDBOOK ON ENGINEERING. 269 

These valves are small and light ; each admits and cuts off 
the steam simultaneously at four openings ; each works in com- 
plete equilibrium; their line of draft is central, so that unequal 
wear is entirely avoided. 

To set the admission valves, — Place the engine on one of its 
dead centers as explained on page 228. Then raise the governor, 
bringing the center of the block between the centers of the 
trunnions of the link. 

With the g-overnof remaining up, set the valve that is about 
to open, giving to it a lead of from ■^-^" to -^^" ^ according to 
the size of the engine. High speed requires considerable lead. 
Repeat this for the other valve on the opposite center. 

On letting" the governor down, the crank remaining on the 
dead center, it will be seen that the valve is moved a short dis- 
tance. This motion of the valve, produced by moving the block 
from the trunnions to the extremity of the link while the crank 
stands on the center, is the same in amount on either center and 
takes place in the same direction ; namely, towards the crank. 
Its effect is, therefore, to cover the port nearest the crank and to 
enlarge the opening of the port farthest from it ; so that the lead, 
which is equal at the earliest point of cut off, is at the crank end 
of the cylinder gradually diminished, and at the back end increased 
in the same degree as the steam follows further. 

The effect of this is to equalize the opening and cut-off move- 
ments, so that, on setting the governor at any elevation whatever 
and turning the engine over, the openings made and the points of 
cut-off will be found to be identical on the opj^osite strokes, from 
the commencement up to the maximum admission. This differ- 
ence in the lead is also singularly adapted to the difference in the 
piston velocity at the two ends of the cylinder. 

In case the indicator shows that the lead of either admission 
valve requires to be changed, this is done without opening the 
chest, by lengthening or shortening the stem at the socket of 



270 HANDBOOK ON ENGINEERING. 

its guide, bearing in mind that each valve moves towards the 
middle of the cyclinder to open its port. 

To set the exhaust valves, — These have an invariable motion, 
and are admirably adapted to their purpose. They are set so as 
to open before the end of the stroke enough to give ample lead, 
and close again when the piston is on the return stroke, early 
enough to effect the required compression. 

All the valves are held between pairs of brass nuts, of which 
the inner one is flanged. These nuts must be securely locked, 
and should be so set upon the valve that it is free to adjust itself 
between the nuts while yet sufficiently tight that no ' ' lost motion ' ' 
exists. To avoid the consequences of a mistake, care should be 
taken, before closing the valve chests, to turn the engine slowly 
through an entire revolution, while the movements of the valves 
are carefully watched, so as to insure that they have not been so 
set as to bring the valves or their nuts into contact with the ends 
of the chest at the extremes of their movements. 

The governof* — The Porter Governor, original in its type, 
stands unexcelled as adapted to stationary engines, requiring close 
regulation. The active parts are very light, the power being- 
derived from a high rotative speed, causing a sensitiveness in its 
movements that will arrest fluctuations and produce uniformity in 
the running of the engine. It has been so perfected that at the 
present day it is easily adapted to the requirements of any class 
of work necessitating a governor, and is especially desirable for 
an engine where a steady speed is necessary. 

The speed of this governor being constant, makes it equally 
efficient upon an engine running either at a high or low number 
of revolutions. That is to say, the speed of engine can be 
altered from time to time by changing the governor pulley, the 
governor itself continuing to run at the same speed and under the 
same strains, and being stationary, it is always open to observa- 
tion. Whereas, any change in speed of engine with the wheel or 



HANDBOOK ON ENGINEERING. 271 

shaft governor, increases or decreases the initial strains upon all 
the parts of the governor, and they have to be adjusted accordingly. 

It is manufactured and sold separate from the Porter- Allen 
engines. 

How to tighten the side boxes of the main bearing;* — This 
is done by drawing up the wedge with the bolts by which it is 
suspended from the cap. The time to do this is when the engine 
is running and the freedom of the journal between its side boxes 
can be felt. The engineer can then draw up the wedges to take 
this out as much as he deems prudent. 

DIRECTIONS FOR SETTING AND RUNNING THE PORTER= 
ALLEN STEAM ENGINE. 

The foundation* — This should be made of concrete, hard 
bricks or stone laid in cement. Bricks are preferred on account 
of their rectangular form and of the more perfect bond they 
make with the cement. Stones of irregular form are sure to have 
the cement bond broken and to spread under the strain of the 
bolts. The bricks should be wet, and the cement washed into 
every course. 

Time should be allowed for the cement to set before any weight 
is put upon it. A week, at least, is required for this purpose ; a 
month is none too long. 

Heavy cut stone is ornamental for a coping, but not essential 
where there is a bed-plate ; the bed-plate of an engine being not a 
mere name, but a reality 

A foundation plan for locating the bolts should be made for each 
engine. The bolts should have some play in the masonry. The 
best way of insuring this is to inclose each bolt in a wooden box 
of half -inch stuff, about sixteen inches long, which is drawn up 
as the courses are added and removed entirely before the engine 
is placed on the foundation, so the bolt holes may be poured full 
of cement after the setting is completed. 



272 HANDBOOK ON ENGINEERING. 

Under ordinary circumstances, a foundation built to the plan 
furnished is ample to hold the engine still ; bub when it must be 
built on soft ground, or on sand or loose gravel, or must be carried 
up through abasement or cellar, it should be extended at the base 
lengthwise in each direction. Sometimes, both these obstacles to 
stability are met with, when the foundation should be extended as 
far as practicable, and at one end, at least, tied to a wall quite 
up to the engine-room floor. The builders of the engine should 
be consulted in such cases. 

Setting the bed* — This setting is done in the usual manner, 
by a line through the cylinder, which is bolted at the end of the 
bed in alignment with the guides. In case the cylinder is not 
yet in place, it is represented by the bore, in the head of the bed, 
and the line is to be continued midway between the side rails of 
the lower guide bars. 

The guides lie in one plane and are to be used for leveling the 
bed in both directions. 

The base of the bed is not brought in contact with the founda- 
tion. Thin parallel packing pieces are to be placed on each side 
of each bolt and under each end of the main bearing, and the bed 
must bear equally on all these, when the guides are level in all 
directions, before any strain is put on the bolts. After these have 
been tightened and the guides are finally found to be level, the 
broad flange of the bed is brought to a general bearing on the 
foundation, by running sulphur under it, or by caulking with 
iron borings wet with water made only slightly acid with sal- 
ammoniac. 

Settingf the shaft* - — lu placing the shaft in position, three 
requirements must be observed. First, to place it at a right 
angle with the axis of the cylinder. Second, that it shall be level. 
Third, that it lies fairly in its bearings. It is readily squared. 
The crank disc is finished on the shaft centers after the 
pin has been set, so that its rim is on the opposite side equally 



HANDBOOK ON ENGINEERING. 273 

distant from its center line, the shaft is square. It is leveled by 
plumbing the crank disc. When thus set it will lie fairly in the 
main bearing ; and if the outer bearing has been correctly set, it 
will lie fairly in that also. This is tested by rotating the shaft 
entirely dry. Brightened rings will show what parts of the 
journals have found bearings, and on lifting the shaft, bright 
spots on the babbitt metal will show where these bearings w^ere. 

The boxes are slightty larger than the journals and so the lat- 
ter should bear along the center of the lower box and not on the 
sides. 

The journals of the shaft if set as here directed will, with 
ordinary lubrication, run cold from the start. Should the shaft 
ever get out of line, it may be squared by gauging between the 
rim of the crank disc and bosses provided on the bed. 

SPECIFICATIONS FOR CENTRALLY BALANCED CENTRI= 
FUQAL INERTIA GOVERNOR. 

It is difficult to say just what is the most important part of 
a modern steam engine, but certainly its governor is among the 
very first. Here then is my idea of what they should be : — 

First. The governor must so regulate the speed of the engine's 
I'evolutions that when starting or stopping it shall not ' ' pound ' ' 
or knock, which means some danger, considerable wear and much 
annoyance. 

Second. It must so regulate the engine's speed when in service, 
that when 125 per cent of its rated capacity be instantly thrown 
upon the engine, the change in speed will not be more than li per 
cent greater or less than the constant speed ; and that if the same 
load be instantly thrown off the engine, the variation shall, in that 
case, be no greater than one per cent. 

Third. That the governor must show every evidence of stability 
or ability to have all descriptions of break loads thrown on or off, 

18 



274 HANDBOOK ON ENGINEERING. 

or both, without " racing " or " weaving " beyond li per cent of 
constant speed. This is to insure against accident and expert 
assistance. 

Fourth. Should any part of the governor or its attachments 
break or become disconnected, the device must not do otherwise 
than to bring the engine to a full stoj). 

Fifth. All the parts of the governor must be light, yet of finest 
materials, to save wasted energy and yet insure reliability. 

Sixth. The construction must be such that during all ranges of 
cut-off, the parts shall remain at all times in perfect balance. 
" Out-of -balance " almost more than any other one difficulty 
has prevented the full success of wheel governing engines, there- 
fore, this feature must be eliminated. No device obviously inca- 
pable of constant balance should be considered unless that long 
sought and potential factor of fine running is to be sacrificed with 
open eyes. 

Seventh. All parts subjected to transmitting strains must be of 
steel. 

Eighth. All transmitting bearings must be j)rovided with 
hardened and ground to gauge steel pins, each of which must be 
furnished with movable phosphor bronze bushings to save wear 
and enable quick and interchangeable repairs. 

Ninth. Springs must be of best quality and made with screwed 
"plug" connections. The bending of the spring into hook or 
eye for connecting will not be permitted. 

Tenth. Governor must b6 so designed and provided with mov- 
able weights, that the speed may be diminished or increased 
graduated amounts without disturbing otherwise the adjustment 
of the mechanism. 

Eleventh. Any governor so designed as to accomplish regula- 
tion clause primarily, and at the same time fulfills all other 
requirements will naturally receive i^reference over other devices, 
which evidently fairly accomplish regulation but fail in other 



HANDBOOK ON ENGINEERING. 



275 



exi^ectations, and yet apparently have only lower first cost as a 
defense. 

The Armington and Sims Engfine^ as is well known, is of the 
high speed type, and in its earlier form was designed with double 
eccentrics, one inside of the other. These eccentrics are operated 
by the shaft governor, and the compound motion produced by the 
movements of the two eccentrics is such that the valve has equal 
lead for all points of cut-off. 




Valve Gear of the Armington & Sims Automatic Engine. 



The method of setting the valve is very simple, for all engines 
of this make are sent out with the valve stem and slide marked at 
points C and B in the sketch, and these points should be set just 
three inches apart. The following are the directions which the 
builders supply : — 

" If the distance between B and G is just three inches you will 
know that the valve is all right. If, however, you wish to put in 
a new valve and adjust, then remove the steam-chest cover and 
place the engine on the center as follows: Place line marked A^ 
which is on the crank pin side, with line on opposite side of rim 
marked F (not shown in drawing), level with engine; now take 
out, or loosen up the springs and block the weights out so that 
the distance between^weights and pin at D E Y>ill be | of an inch ; 
adjust the valve-stem at the guide so that by turning the engine over 



276 



HANDBOOK ON ENGINEERING. 



from one center to the other the lead will be the same at both 
ports ; then make a new mark distinctly on the valve-rod, so that 
the distance B C will be the standard three inches. 

" It is not possible to reverse the direction of running without 
sending to the factory for new parts. The governor is not con- 
structed so that one set of parts can be used for running both 
ways." 

THE CARE AND MANAGEMENT OF HARRISBURQ ENGINES. 

It is essential to the successful operation of any high-class and 
expensive machinery, that the person in charge be gifted with a 
fair degree of intelligence and alertness, and while I have at- 
tempted to formulate a few rules as a guide to the person in 




Sectional Elevation of Harrisburg Standard Four-Valve 
Tandem Compound Engine. 



charge of an engine, the fact must not be overlooked that a great 
deal depends upon the skill and judgment of the operator himself, 
and that it is manifestly impossible to give rules other than of a 
general character and which may frequently have to be modified 
to suit the different conditions that may arise. However, tbe 



HANDBOOK ON ENGINEERING. 277 

following are some suggestions for the convenience of operating 
engineers : — 

When engines of these styles have been properly erected, the 
steam, exhaust and drain connections completed, and the piston 
and valve rods packed, the operator should be careful to see that 
all parts are in proper position and firmly secured. 

The bed should be thoroughly cleansed inside and a good 
quality of machine oil poured into the reservoir beneath the crank, 
until it is just in contact with the crank disc. 

A mineral oil only should be used, and of medium viscosity. 
Fill the eccentric lubricating cup and flush the main bearings 
with the oil. 

The cylinder lubricator should be filled with a first-class qual- 
ity of cylinder oil, of heavy body. 

The best oils obtainable are the most economical, without 
question. 

Careful preparations before starting engine* — The cylinder 
and steam chest drain valve should now be opened, and the 
throttle valve carefully started just enough to allow a small quan- 
tity of steam to flow through the cylinder and out through the 
drain pipes, but not enough to actually start the engine in 
motion. 

After the cylinder and valves have been thoroughly heated 
and any water standing in the steam pipes thus blown off, start 
the oil flowing in the cylinder lubricator cup. A general survey 
of the engine should now be taken and if everything is found to 
be in proper condition, carefully open the throttle valve and bring 
the engine gradually up to speed, when it should be noted that 
the governor is controlling the machine. Examine the bearings 
and eccentric to see if the oil is flowing properly, and make sure 
that every part is operating smoothly, after which the drain valves 
may be closed. 

Adjtistments for wea^« — When the engine has been in opera- 



278 HANDBOOK ON ENGINEERING. 

tion long enough to necessitate the adjustment of the working 
parts, care should be used to avoid adjusting them so close as to 
cause heating, and the following general rules should be 
observed : — 

The caps on the main bearings should always have sufficient 
liners underneath to enable the nuts on the bearing studs to draw 
the' cap down solidly upon them and not pinch the shaft, which 
should be free to revolve in its bearings without unnecessary play. 

Adjustment of crank-end connectingf tod* — In adjusting the 
connecting-rod box at . the crank pin end the same general rules 
should be observed regarding the liners under the cap, the large 
nuts drawn solidly upon it, the small nuts firmly jammed, and 
the cotter pins placed in position. 

The adjustment of the box should then be tested with a lever 
about 12 inches in length, the adjustment being so made that 
with a lever of this length the operator can easily move the end of 
the connecting rod sufficiently to take up the side play between 
the flanges on the crank pin and the ends of the box. The 
adjustment should never be made so close that this side movement 
cannot be observed. 

Adjustment of cross-head pin box. — The adjustment of the 
connecting-rod box at the cross-head pin end should be made by 
removing the name plate from the engine frame and placing the 
crank on the center nearest the cylinder, then with the wrench 
provided for that purpose, slack off both wedge screws at the 
upper and lower sides of the connecting rod, and draw the wedge 
up until it is solid against the box, then slack off that screw 
about a sixth of a turn and draw up the other so as to firmly lock 
the wedge ; this method prevents the box from pinching the 
cross-head pin. 

The ** flats '' on the cross-head pin should always be at the 
top and bottom to avoid wearing a shoulder, and the nut on the 
end should be drawn up firmly, but not so much as to spring the 



HANDBOOK ON ENGINEERING. 279 

bosses of the cross-head together, nor yet enough to make the 
box tight on the ends. 

I prefer adjustment of the cross-head in the guides made by 
liners of paper or tin, placed between the bronze shoes and the 
body of the cross-head. 

Adjustment of cross-head shoes* — In order to do this it is 
necessary to remove the pin and the end of the connecting rod 
from the cross-head, and with a wooden lever placed in the pin 
hole turn the cross-head until the shoes are out of the guides, 
then remove the shoes and place the liners beneath them. Care 
should be used that the cross-head does not fit the guides too 
closely, and that it can be moved freely with a short lever from 
one end of the guides to the other, while disconnected from the 
connecting-rod. 

The cross-head should, never be run very close and should 
always be free enough to allow long and continuous runs without 
causing the top of the bed over the guides to feel uncomfortably 
warm to the touch. 

Attachment of cross-head to piston rod* — When making any 
adjustments of the cross-head, it is well for the operator to assure 
himself that the lock nut, which prevents the piston rod from 
turning in the boss at the end of the cross-head, is securely in place. 
All but the largest Harrisburg engines are tested under steam 
before leaving the works, and the valves set with the indicator. 

The distance from the cylinder head end of the valve, when 
the crank is on the center nearest the cylinder, is marked on the 
end of the cylinder directly underneath the steam chest cover. 
If from any cause the valve should become deranged, place the 
crank on the center described and with a scale or rule, see that 
the valve position corresponds to the dimension marked on the 
end of the cylinder ; and if out of position, it can easily be re- 
adjusted by means of the device provided for that purpose, at the 
outer end of the valve stem. 



280 HANDBOOK ON ENGINEERING. 

On the Hamsbufg Ideal Engines, where the ball joint con- 
nection is used between the valve stem and the eccentric rod, the 
wear is followed up by filing the end of the bronze connection 
that the cap is screwed against, which holds the ball in place. 
And on the Harrisburg Standard Engines, where the ram box 
connection is used, the adjustment is made by filing the half of 
the bronze box, which is attached to the end of the eccentric rod 
that connects with the ram. 

Adjustment of eccentric strap* — The eccentric strap adjust 
ment is made by liners placed between the halves of the strap and 
double nutted bolts. When adjustment is necessary, the other 
end of the eccentric rod should be disconnected and after drawing 
up the strap bolts it should be tested by giving the strap a half 
revolution about the eccentric. If it is found that the friction 
between the strap and eccentric is sufficient to support the weight 
of the rod, the bolts should be loosened until the strap moves 
freely without lost motion. The double nuts should then be 
locked and the cotter-pins replaced in the ends of the bolts. 

How to alter eng-ine speed* — The governor used on all Har- 
risburg Engines is the Centrally Balanced Centrifugal Inertia 
Type. A few words of explanation may be of service to oper- 
ating engineers. 

The weight arms are constructed with differential weight 
pockets, to allow of a considerable range of speed adjustment 
without altering the tension of the springs. If an increase in 
speed is desired, remove weights of an equal thickness from the 
weight pockets of the levers, and add weights of an equal thick- 
ness to obtain a decrease , in speed. If an increased speed 
causes the governor to " race " or " weave," move the clamp in 
the slot, to which the outer end of the spring is attached, farther 
from the small end of the weight lever. If this does not entirely 
correct this sensitive condition, screw the plug into the spring 
until the racing ceases. If the decrease of speed so obtained 
renders the governor too sluggish in action, move the clamp in the 



HANDBOOK ON EN(4INEERTNG. 281 

slot in the opposite direction. Jf this does not improve the regu- 
lation, and the speed is lower than desired, add weights of an 
even thickness, increasing the spring tension until the proper 
speed is obtained. The main lever bearings which are equipped 
with anti-friction steel rollers, should be oiled about once a week, 
and taken out and cleaned about once a month ; the other joints 
fitted with compression grease cups, should be treated in the same 
manner. About once a month, also, the springs should be dis- 
connected and the governor and valve gear tested by hand, to make 
sure all joints are working freely. 

The foreg'oing will apply also to the Harrisburg Standard and 
Ideal Compound Engines, and, in general, to the Harrisburg Self- 
Oiling Four Valve Engines. Adjustment for wear in the valve 
gear connection of the latter type of engines is obtained by filing 
the halves of the bronze boxes on the ends of the rods connecting 
the valves with the wrist plates and rocker arms, and on the 
wrist plate and rocker arm pins, by means of bronze shoes let 
into the sides of the bearings, the wear being followed up by the 
screws provided with lock-nuts, and all bearings lubricated by 
means of compression grease cups. The Harrisburg Corliss En- 
gines, of the larger sizes, are provided with quarter boxes in the 
main bearings with wedge and screw adjustment, and are built self- 
oiling or otherwise, according to size. The lubrication of the prin- 
cipal bearings is accomj^lished by means of oil cups, and the valve- 
gear connections by means of conveniently arranged grease cups* 

Mcintosh and seyhour high speed engine. 

How to set the valve. — When the. engine is sent out from 
the shop, the valves are set and trammed with three inch tram 
from the valve-rod to the valve-rod slide at C D, and from the 
eccentric rod to the eccentric rod head at E F, on the valve-slide 
end, and a tram is furnished with the engine, or a new tram can 
be made with exactly three inches distance between the points, 
which will suffice. 



282 



HANDBOOK ON ENGINEERING. 



In case tlie tram marks become lost, or, owing to wear of 
the valve gear, the length of connection is altered, the proper 
procedure is to j^ut the engine on one center, and then on the 




A Sectional Cut of Mcintosh and Seymour High-Speed Engine, 
Showing Valve and Governor. 



other, and observe the leads which occur when the governor is in 
the normal position of rest, as shown. The lead on the crank end 
should be three times as much as the lead on the head end, if the 
connection between the valve and eccentric is of proper length. 

When the valve is set this way, the cut-off on the two ends 
of the cylinder will be approximately equal at one-quarter cut-off 
on the smaller size engines having inside governors. 

Preliminary to adjusting connections between the valve and 
eccentric, care should be taken that the mark on eccentric G H\ 
corresponds to the mark on the pendulum. 

In examining the steam leads, as described above, it should 
be noted that the surface B on the valve has nothing to do with 
the steam distribution, but it is merely to give ample wearing sur- 
face, and that the steam is admitted to the cylinder through the 
port which is between B and the steam edge which is at A^ and 
the lead should be measured between this steam edge and the 



HANDBOOK ON ENGINEERING. 283 

edge of the port leading to the cylinder. On engines of larger 
size having outside governors, a similar method should be em- 
ployed in setting the valves, except that the trams are four inches 
from point to point, and should be used between the valve-rod 
slide and valve-rod, and the eccentric rod and the eccentric 
rod head at governor end, instead of slide end, as above. 

INSTRUCTIONS FOR STARTING AND OPERATING IDEAL 
ENGINES. 

Before starting engine* — Open cylinder cocks and throttle 
valves sufficiently to warm the cylinder and valve. Place sufficient 
oil in the basin under the crank so it will stand one inch above the 
bottom of crank discs. When receiving a new engine from the 
shops with visible stuffing-box and water drain, before you fill 
the crank case with oil, previous to starting, pour water in opening 




Fig, 1. 

in frame into pocket under piston rod stuffing-box, until water 
overflows through trap connected therewith attached to outside of 
frame. Fill cylinder lubricator and start it to feeding. Fill oil 



284 HANDBOOK ON ENGINEERING. 

pump, and pour engiue oil into pocket on nuiin bcjirings. Fill 
eccentric oiler and start it feeding. After the steam chest and 
cylinder are warm, turn the engine over by hand to see that all is 
free and right to start. 

Open the throttle valve gradually, start engine slowly. After 
the engine is up to speed, pump five or six strokes of oil into 
cylinder with oil pump. The oil should flow in streams through 
both pipes on the crank cover into the j^ockets of the main shaft 
bearings. 

This oil passes from the maiu bearings through the crank pin 
and is distributed over cross-head pin and slides. Occasionally 
clean out the oil passages in crank pin. 

Supply^ as needed, a little fresh oil to the basin, and if the 
oil in the engine bed becomes thick, gritty or dirty, so as not to 
flow freely through oil passages, draw it off and replace with fresh 
oil. Filter the old oil and use it over continuously. Use a pure 
mineral oil that will not thicken by the churning it receives. 

Serious damage and cutting of the cylinder and valve will 
result from allowing the lubricator to cease feeding, even for a 
few minutes. If your engine is a new one from the shops, feed 
plenty of oil through the lubricator and oil pumj) for the first 
few weeks after starting. Use one drop of oil per minute for each 
ten horse-power, or ten drops per minute for 100 horse-power 
engine, for the first thirty days ; after which, one-half this amount 
will be suflacient, if the oil is of good quality. If your boiler is 
priming or foaming, use double the quantity of oil to j^rotect the 
cylinder and piston from cutting. A little graphite fed into 
cylinder is very beneficial. 

The governor* — Fill the cuj^s on governor bearing with grease 
and give the cap J turn every day. Screw the cap to the stuflftng- 
box on dash pot loosely, only using your hand to turn the cap. 
The governor should be taken apart every two or three months 
and bearings cleaned with coal oil to remove gum. If governor 



HANDBOOK ON ENGINEERING. 285 

has a dash pot, it should be refilled with glycerine once or twice 
a year. Oil may be used in the dash pot in place of glycerine, 
unless the engine is in a cold room where the oil is liable to 
congeal. To refill dash pot, unscrew cover on end. 

In taking" the governor apart, allow the sliding block which 
holds the end of the governor spring to remain with its outer edge 
on a line with a mark across the face of the slide, and in re- 
adjusting the spring, place the same tension on it as before, 
which can be ascertained by measuring the length of the thread 
through the nuts before slacking up the spring. If you have 
trouble with springs breaking it is because you are working 
them under too much tension. The speed of the governor is 
changed by moving the weight on the lever. 

To increase the speed of the engine, move the weight on the 
governor lever near to the fulcrum pin. To reduce the speed, 
move the weight out toward the end of the lever. Tightening the 
spring will also increase the speed, but will cause the engine to 
" race," unless at the same time the block which holds the end of 
the spring, is moved toward the center of the wheel. The proper 
way to change the speed is by moving the weight, allowing the 
spring to remain in its marked position. 

Moving the blocks which holds the spring, towards the rim of 
the wheel, will make the governor more sensitive and regulate 
more closely ; but if moved too far, this will cause the governor 
to " race." Moving the block towards the hub of the wheel has 
a tendency to stop the " racing," but if moved too far the speed 
of the engine will be reduced with the increased load. If any of 
the bearings of the governor bind, or require oiling or cleaning, 
the governor will " race." These bearings should be kept clean 
and in good condition and the stuffing-box to the dash pot must 
not be screwed up tight, as that will cause the governor to " race " 
when set for close regulation. 

The face of the slide is marked with a line where the outer 



283 HANDBOOK ON ENGINEERING. 

edge of block which holds the spring should be. Figures stamped 
on the face of the slide, give length of end of eye-bolt extending 
through nuts. This gives the right tension to the spring. 
Tightening the spring will give closer regulation, but will cause 
the governor to " race " if the spring is too tight. " Racing " 
caused bv over-tension of spring, can be stopped by moving block 
nearer to center of wheel. 

To set valve. — Should you wish to ascertain if the steam 
valve IS properly set, proceed as follows : Take off the cover or 
elbow on outer end of steam chest, so you can have access to end 
of valve. Turn the engine over until the valve has traveled as 
fiir as it will go towards end of steam chest. Then measure from 
the end of steam chest to the end of the valve, and this distance 
should be represented by the figures in inches and fractions 
on end of steam chest. If measurements do not agree, set valve 
by screwing the valve stem at the ball joint. 

Square, braided flax packing is the best kind for piston rod and 
valve stem. Don't screw the glands up tight; allow them to leak 
a little. The valve stem has only exhaust steam — don't pack it 
tight. Screw it up by hand only. Screwing the piston rod gland 
lip tight may cause the piston to thump or pound the cylinder, 
and heat and cut the piston rod. 

Safety caps* — The safety caps attached to drip valve under 
the cylinder are intended to break, in order to save damage to the 
engine if water enters cylinder. They will protect the engine 
from breaking if the amount of water is not too large to pass 
through the valves and pipes. If they break, they have accom- 
plished their purpose and new ones should be attached. 

Eccentric. — Take up lost motion by reducing the brass liners 
between the lugs on eccentric strap, and unscrew and dis- 
connect the ball joint on the eccentric rod to see that the eccen- 
tric strap will turn freely on the eccentric. If a close fit it will 
heat, out, seize and break the eccentric rod or valve stem. Allow 



• HANDBOOK ON ENGINEERING. 287 

the eccentric strap to run loose ; no harm if it knocks a little. 
It will not wear out of round on account of running loose ; it is 
dangerous to run with the strap snug. 

Ball joint, — Take up lost motion in the ball joint, on the valve 
stem, by unscrewing the joint at eccentric rod and turning or 
filing off the face of the brass part attached to the valve stem, 
so as to allow the male part to screw in a greater distance. 

Connecting rod* — Take up the lost motion on the crank pin 
bearing b}^ removing the cap and taking out two of the steel 
liners ; take one from each side, put the cap back and set the 
nuts up snug. Disconnect the cross-head end of the rod by re- 
moving cross-head pin, and try lifting the rod up and down to 
see that it does not pinch the crank pin. If it pinches the pin 
when the bolts are drawn up snug, place the liners back or substitute 
thinner ones. Always screw the cap back solid on the liners, and 
keep in sufficient liners so the cap will not pinch tbe pin when the 
bolts are screwed down snug. Never run the engine without 

HAVING THE CAP SCREWED UP SOLID AGAINST THE ROD, with 

liners between if needed, to make the proper fit. If you remove 
some' of the liners be sure to take out an equal amount from each 
side, for if you take out more on one side you are liable to throw 
the cap at an angle in tightening up the bolts, which, in time, 
will cause the bolt to break and is liable to wreck the engine. 

The brass in the cross-head end of the connecting rod is set up 
hj a wedge. This wedge is drawn down by the steel bolt until 
the brass is forced solid against the shoulders in the end of the 
connecting rod, which prevents any movement of the brass. 
The upper bolt is used to lock the wedge in position ; also in 
withdrawing the wedge when the brass is to be removed. 

To take up lost motion in the cross-head end of the connecting- 
rod, remove the brass and file an equal amount, even and square, 
from each edge of the brass, so as to allow the brass part to come 
up to the pin. When filing the brass, try the pin in the rod 



288 HANDBOOK ON ENC4INEERING. 

and do not file enough to allow the brass to pinch the pin when 
the wedge is screwed doum solid. If, by mistake, too much is 
filed off, i3ut in a sheet of copper or sheet brass liner, so the 
wedge may be drawn snng without pinching the pin. 

Cross-head* — For adjusting the lower cross-head slide, take 
out the cross-pin, turn cross-head J round with the lower 
brass slipper opposite oi^ening in engine frame ; loosen nuts and 
insert paper or thin metal strips between cross-head and slipper. 
The top slide will never require adjustment. The lower slide 
should run five years before requiring liniug or adjustment. 
Turn the cross-head pin i way around every three months. This 
will prevent it wearing out of round. 

Main bearings* — To take up lost motion in the main shaft 
bearings, remove the cap and file, scrape or plane an equal 
amount from each of the babbitt metal liners or strips which are iu 
the main bearings under the inside edge of the cap. Remove the 
metal evenly, so the liners will remain of equal thickness at each 
end. Do not remove enough from the liners to allow the cap to 
l^inch the shaft when the nuts are screwed down snug. If, by 
mistake, too much metal is removed, put in paper strips on top of 
the liners so the cap can be screwed down solid without pinching 
the shaft. You can tell when the cap pinches the shaft by turn- 
iug the engine over by hand ; it will not turn freely when the cap 
is too tight. With proper care the main bearings will run two 
years before requiring adjustment. None of thp: bearings of 

THE ENGINE SHOULD BE SO TIGHT AS TO PREVENT TURNING THE 

ENGINE FREELY OVER BY HAND. Always tcst the engine in this 
manner after adjusting bearings. 

If a bearing- heats, stop the engine immediately, take out shaft 
or box, clean out the cuttings, scrape smooth, clean out oil pass- 
ages and run bearings loose. 

Heating or cutting v:iH never occur if liners are put in so caps 
cannot be set up to pinch the bearings and they receive proper 



HANDBOOK ON ENGINEERING. 



289 



lubrication with oil free from grit or dirt. After adj listing- any 
of the bearings, run the engine for a few minutes ; then stop the 
engine and feel the bearings which have been adjusted to see if 
they are running cool. This precaution may obviate having to 
shut down your engine while performing regular duty. 

Do not allow yoin' engine to run with bearings so loose as to 
thump or pound, as this will cause the bearings to wear out of 
round. If the shaft or wheels run out of true or wabble, it is 
because the main bearings are loose and should be taken up. 
The engine will run smooth and noiseless if bearings are properly 
adjusted. 

THE STEAH CHEST. 

Fi^. 2 shows a section through cylinder and valve. The steam 
chest is bored out and fitted with a pair o' cylinders or bushings. 




Fig. 2. 



which have supporting bars across the ports, to prevent any pos- 
sibility of the valve catching upon the ports. 

The valve is of the hollow piston type — a hollow tube with a 
piston at each end. The live steam is entirely upon the outside 

19 



290 HANDBOOK ON ENGINEERINa. 

of this iMstoii, pressing equally on each end ; the exhaust steam is 
entirely on the inside of the piston, so the valve is perfectly bal- 





Fig. o is a Tandem Compound. 

anced and can easily be moved by hand when under full boiler 
pressure. 

Fig* 4 is a cross-section of cylinder and valve of the Tandem 
Compound engine. The cylinders of the Ideal Compound engine 
in Fig. 4, the stuffing-box between the two cylinders, is dispensed 
with entirely. It is replaced by a long sleeve of anti-friction 
metal. This sleeve is light and free to adjust itself central with 
the rod. Grooves are turned on the inner surface, so as to form 
a water jjacking. 

Both valves of engine are controlled by the same governor on 
the same stem, moving together and varying in stroke as the load 
and steam pressure vary. This gives the advantage of automatic 
cut-off in both cylinders and dispenses with the complication of 
double eccentrics, rock arms, slides and stuffing-boxes. 

The high-pressure cylinder has a piston valve, same as used in 
all ideal engines. For the low-pressure valve in order to bring it 



HANDBOOK ON ENGINEP:RING. 



291 



into line with the high-pressure valve and keep clearance spaces 
at minimum, which thus gives a quick and wide opening at the 
beginning of the stroke, in order to reduce the pressure on 
exhaust end of high-pressure piston. 




Fig. 4. 

The cover of this valve is held in place by springs and will 
lift and prevent excessive pressure in the cylinder from water or 
other causes. 



FOR INDICATING IDEAL ENGINES. 

The illustration (page 292) shows the reducing motion at- 
tached to engine ready for taking indicator cards. 

To apply the Ideal Indicator Rig: Screw slotted stud in 
cross-head pin, first removing the cap screw. Set the slot per- 
pendicular to line of motion of cross-head. Set cross-head 
exactly in center of its travel. Fasten on top of bed where oil 
funnel is placed, first removing the oil funnel. 

Lever should be adjusted so it will travel in slot without strik- 



292 



HANDBOOK ON ENGINEERING. 



iug bottom, or passing out at top. Make sure that lever will 
travel freely in slot without binding. Select a hole on string- 
carrier that will give the necessary motion to indicator drum. 




FiQ 



With string attached from indicator thi^ough hole, so adjust this 
carrier that lines drawn on polished surface shall come exactly 
parallel with string. Make all adjustments while cross-head is 
in center of its travel. 



POINTS ON STARTING AND RUNNING A WESTINQHOUSE 
COMPOUND ENGINE. 

In the compound engine, the automatic governor is located 
on the shaft inside an inclosed case lilled with oil, which forms 
the center of one band wheel. Its action varies the travel of 
the valve in accordance with the amount of work demanded of 
the engine. The other end of the shaft carries an ordinary 
band-wheel, or combination pulley, of any required diameter and 



HANDBOOK ON ENGINEERING. 



298 



face. Set up the eiigiue as directed, keeping tlie coinl)inatioii 
pulley, or band-wheel, as close to the engine as possiljJe. AVork 
the wheel on by turning it around while the shaft is held station- 
ary. Do not attempt to drive it on. 




The above is a cut of the Westinghouse Compound Engine. 

In otdei* to put on the governor case with its band-wheel, it will 
be necessary to first remove the lid or cover of the case, so as to 
get at the set screws and key way. It is to be put on carefully 
and should not be driven on hard enough to in any way injure the 
shaft. The keys are to be carefully fitted to their places, and 
this should be done by a competent mechanic. It is not pos- 
sible, in every case, for the wheels to be put on the engine to 



294 HANDBOOK ON ENGINEERING. 

which they Ijeloiig iiiid keys lltted in their proper jjlaeeti, I'ur 
various reasons ; therefore, the keys are left as they come from 
the planer, a trifle full of the required size, so that a little filing 
will bring them to a good lit. If the keys are not fitted in well 
and carefully at the start, they may become the cause of a great 
deal of subsequent trouble ; but if this be well done at the 
beginning, there will be no trouble afterwards. It is tlie practice 
of some to tie a tag to each key, designating which one is intended 
for the governor case wheel and for the band wheel. It is im- 
l^ortant they should not be put in the wrong places. If the band 
wheel key should be a trifle too long, no harm will result ; but if 
the governor case key be too long, it will protrude through the 
case and bind the eccentric so that the latter will not have free 
movement across the shaft, and this will seriously attract the 
regulation of the engine. The key in the governor case should 
be from J" to J" shorter than the hub in the governor case, to 
l^revent this possibility. When the keys are well fitted they should 
be driven home with a degree of tightness dejiending on the size of 
the engine, and the set screws should be j^uUed down hard and 
fast to hold them. The keys are not intended to fit top and 
bottom, but must fit exactly sideways. 

After the governoi* case with its wheel is properly located on 
the shaft, the key fitted and set screws pulled down hard and fast, 
the governor case lid is to be put on, having a paper gasket, both 
on its outer edge and at the hub, to prevent leakage of oil past 
these surfaces ; and it is to be bolted up tightly in its place, and 
the governor case completely filled with cylinder or Dalzell crank- 
case oil, through a connection provided for this j^urpose. 

Turn the eng-ine over by hand to make sure that everything is 
free. Before starting the engine for the first time, oil both pistons 
thoroughly by taking off the relief valves and pouring oil into the 
ports. This oil will work through the valve and oil it also. 
Swina; aside the bonnets from the crank case, and see that the 



HANDBOOK ON ENGINEERING. 295 

latter is clean and free from the cinders and dust of travel, which 
generally find their way into the interior. When found to be per- 
fectly clean, supply oil and water according to the following 
directions : Pour in' water until it makes its appearance at the 
outlet of the overflow cup ; then pour in one gallon of Westinghouse 
crank-case oil for every 10 H. P. of the rating of the engine for 
the smaller compounds, and about half this amount for the larger 
ones. This will raise the water and oil in the interior to such a 
level as to almost touch the crank-shaft, so that the connecting 
rods will be plunged into the liquid at every revolution. Take off 
the eccentric strap, clean it thoroughly, also clean the hollow 
eccentric rod, then oil and replace it. Be liberal in the use of oil 
all over the engine, at least for the first few days. Remember 
that there are two large cylinders and a valve to be lubricated and 
that the low-pressure cylinder gets its oil only through the high-pres- 
sure cylinder. The engine should now be ready to start. Fill 
the automatic lubricator on the steam pipe with good cylinder 
oil ; fill the side oil cups over the main bearing with Westing- 
house crank-case oil, and open the drip-cocks over each main 
bearing, so that the drip is continuous and regular at the rate of 
about 2 to 10 drops per minute from each cup, according to the 
size of the engine. If undue service is required of the engine, so 
that the main bearings show signs of heating, the amount should 
be increased. Start the automatic lubricator; give the eccentric 
strap some direct lubrication from a squirt can, and start the cup 
over the rocker arm to feeding from each cock. 

To start the engine* — the throttle valve being closed, open 
the drain cocks in the throttle-valve and steam and exhaust pipes, 
blow them out thoroughly and then close them. Open both cylin- 
der drain cocks ; raise the check valve on the crank case by set- 
ting the handle down ; open the by-pass valve. Turn the engine 
round until the high-pressure piston is on the upper center. Now, 
open the throttle-valve slightly, for the purpose of warming up the 



29(1 HANDBOOK ON ENGINEERING. 

steam-chest aud valve equally, as otherwise the valve, by heating- 
quickest, may expand and bind. The engine being on its center 
will not start. When sufficiently warmed up, say in three minutes 
by your watch, close the throttle value for an" instant and bar the 
engine oft' the center. Then open the throttle-valve quickl}^, but 
not too far, which will insure the engine passing the first center. 
As soon as the engine is up to speed, close the by-pass valve 
tight and keep it closed thereafter. When the water is thor- 
oughly worked out of both cylinders, close the cylinder cocks 
and keep them closed, and at the same time, close the check valve 
and open main throttle-valve gradually until it is wide open. 
Never attempt to regulate the speed of the engine by the throttle- 
valve. 

In stopping the engine, open the cylinder cocks, check valves 
and by-pass valve and close the throttle slowly, so as to allow the 
engine to lose speed by degrees. Do not stop suddenly, as the 
momentum of the pistons and fly-wheels, at standard speed, is 
great, and the strain thrown on the connecting rods and crank- 
shaft, in being suddenly stopped, is unnecessary and may, in time, 
become injurious. 

.In genctalf it is well to run a new engine empty (that is with 
no belts on) in order to be certain that everything is right; then, 
if the performance is all right, the belts can be thrown on. 

With a compound engine properly adapted to its work, not 
overloaded, and running under proper conditions, the duty of the 
engineer may l)e said to be merely nominal. Nevertheless, this 
engine, when it requires the attention of an engineer, needs the 
proper kind of attention. One coihpetent man can operate a 
very large number of these engines. What is meant in this con- 
nection by the terms ' ' properly adapted ' ' and ' ' proper condi- 
tions," is: a load corresponding to a mean effective pressure in 
the high-pressure cylinder not exceeding one-half of the boiler 
pressure ; a boiler pressure as high as possible, the engine erected 



HANDBOOK ON ENGINEERING. 297 

in compliance with the directions given, and the directions as to 
lubrication followed carefully. 

The wear is constant in one direction, namely, downward. 
The steam acts only on the upper side of the pistons. The two 
crank-pins are exactly opposite each other. Each piston in its ' 
downward stroke raises the other piston. The direction of the 
wear on all the bearings being downward, the lost motion may be 
considerable without detriment to the quiet running of the engine. 
In starting and stopping the engine, however, the accumulated 
lost motion will cause a noise, inasmuch as this motion is taken 
up at each revolution ; the greater the amount of lost motion, the 
greater this noise will be in starting and stopping. The cause of 
this is apparent ; the crank, while the engine is stopping, must 
pull the piston down and the effect of lost motion then becomes 
similar to that in a double-acting engine. The effect of this 
action is not conducive to good wear or long service. It allows 
a shock to come on the connecting rod strap with con- 
siderable force ; this wear, therefore, should be taken up fre- 
quently, but it can be allowed to accumulate to a greater 
degree than will be possible in any double-acting engine. 
The wear is taken up on both ends of the connecting rod at once, 
by the upper bolt at the lower end. The engineer on opening 
the crank case will see a bolt with a squared end and a lock nut ; 
with the large end of the socket- wrench, he will slack off the lock 
nut, and then with the small end of the wrench he will turn the 
bolt to the left until the brasses come up solid ; then slack off 
half a turn and set up the lock nut. The construction of the rod 
and the way in ' which a single wedge is made to take up both 
ends of the rod at once, is evident from the cut. The piston 
wrist-pins, if worn or cut, should never be dressed off or turned 
down, as they will not fit the bushing or have a proper bearing. 
Order a new pair, and throw the old ones away. When the 
babbitt is about worn out of the main bearing shells, they can be 



298 HANDBOOK ON ENGINEERING. 

re-babbitted and pat back again. The cylinder packing rings 
will, after much wear, become unfit for service, and will allow 
steam to blow past the pistons into the crank-chamber. There 
will be at all times, when the engine is running loaded, a small 
amount of vapor arising in the crank-case. This does not 
necessarily indicate that there is a leakage of steam past the 
pistons, as the heat generated by the splashing of the water on 
the hot pistons and cylinders, and by the leakage of the hot 
water of condensation past the pistons, will heat up the water 
contained in the crank-case, until it vaporizes slightly. New 
packing rings can be easily sprung into place by the engineer. 

The principal duties of the engineer will be to see that the 
automatic lubricator, which oils the cylinders and valve and the oil 
cup over the rocker arm, perform their work properly and regu- 
larly. Feed slowly, drop by drop, according to the requirements 
of the engine. The engineer must also see that the oil tanks on 
the sides of the engine are supplied with oil and fed slowly, drop 
by drop, into each main bearing. 

The inclosed construction of the engine, whereby all oil used 
in lubrication is completely distributed on the wearing surfaces 
and is prevented from wasting, renders it unnecessary for the 
engineer to pay as close attention to this engine as to any other, 
as it, in a sense, lubricates itself. The crank-case bonnets should 
be removed regularly, preferably every morning, as it is the work 
of only a few minutes. The interior of the engine should be 
examined to make sure that no nuts or bolts (of which there are 
the fewest possible number) have worked loose, bushings worn 
out, or lost motion become unduly great ; this internal examination 
is absolutely imperative, at least, once a week. The proper 
drainage of water in the steam j^ipes should demand his attention, 
to prevent any entrainment, resulting from the foaming of the 
boilers or from any other cause. Entrained water is always a 
prolific source of trouble in steam engineering ; it is particularly 



HANDBOOK ON ENGINEERING. 



299 



troublesome in all piston valve engines, even with Westinghouse 
engines, which are provided with water relief valves. The 
engineer should become thoroughly acquainted with his engine so 
as to understand its operation and principle, and be at all times 
familiar with its precise condition. All adjustments being made 
in the shop before shipment, it is unnecessary for the engineer to 
set any valves or take any part in the adjustment of a new engine ; 
but as wear occurs, he must be able *to intelligently make the 
needful adjustments of wearing parts. After an engine has run 
a long time, the downward wearing of the reciprocating parts will 
have the effect of throwing the valve slightly out of adjustment. 
That is to say, it will draw the valve gear downward with the 
shaft, and favor one cylinder more than the other. The valve, 
therefore, will require resetting occasionally, but not at all fre- 
quently. It should be adjusted by lengthening the eccentric rod, 
just the amount to which the shaft is worn downwards. 





MAIN BEARING. 



MAIN BEARING. 



The main shaft bearings are now made adjustable. There is 
a slight difference of construction here in the various sizes, 
occasioned by limited space in the castings ; but they are all 
alike in this respect, that the bottom half of the main bearing is 
stationary, being turned off on its outer shell eccentric with the 
shaft journal and held down firmly by a long set screw on each 



?)00 HANDBOOK ON ENGINEERING. 

side, which [)revents it from rotating or from rattling loose. The 
top half of the main bearing is adjustable downwards, so as to 
follow up any wear either of the babbitted bearing or of the shaft. 
In the 8 and 13x8 and 9 and 15x9 engines, this top half of 
main bearing is adjusted downwards by three set screws located 
at the apexes of a triangle, and the bearing is locked firmly by 
three tap bolts oppositely placed so as to hold it secure after 
adjustment. In the case of all larger sizes of compound en- 
gines, the downward adjustment is made by wedges bearing on 
the inclined tops of the upper half of the bearing. These wedges 
are moved and locked by a tap bolt in each end, which passes 
through and draws against the shell of the crank-case head. The 
top half of main bearing is drawn up and locked in position after 
adjustment by tap bolts which pass down through the top shell 
and are screwed into the bearing. Some of these bolts and wedge 
screws are inside of the crank-case, and adjustment must, there-, 
fore, be made while the engine is standing idle. It is customary 
to mark with an arrow head on the outside of the crank-case head 
to indicate which way the wedge will move to tighten up. 

The proper condition of the compound engine, while perform- 
ing its work, is one of perfect quiet, without leaks of steam past 
any joint and without noise. Any noise in the engine, after it 
has attained full speed, may be immediatel}^ accepted as an indi- 
cation that something is wrong and the engineer should familiar- 
ize himself with it, so as to be able to discover the cause and the 
remedy. Hot bearings may be said to be unknown in this 
engine ; occasionally, however, they have been met with but they 
are always traceable to the use of improper oil ; dirt and grit in 
the oil ; the filling up of oil grooves, or the wearing out of the 
oil grooves in the main bearing shells ; or to worn out or broken 
packing rings in the piston. The eccentric strap is the only point 
liable to run dry, and the engineer should see that the oil cup 
feeds with certainty. All joints in the governor are bushed and 



HANDBOOK ON ENGINEP^RING . 301 

these bushings are provided with sufficient oil holes ; they can 
readily be replaced with new ones when necessary. In replacing 
bushings, always be careful to provide ample oil-holes, the same 
as were in the old removed bushings, and observe the same pre- 
caution in the case of other repairs. 

As above stated, it is the duty of an engineer to know in what 
condition every part of his engine is at all times. All wearing 
parts should be examined from time to time, so they can be re- 
placed before they are entirely worn out and damage is done. It 
is too late to find out that a bushing needs rej)lacing after it has 
been worn entirely through and the pin has cut into the solid 
metal. While the engine is built of the very best materials and 
with the greatest care, and while the means and the opportunity 
for lubrication are the best known, yet it is not claimed that 
it possesses any miraculous virtues by which it will run on for- 
ever without any attention and without repairs. Nowhere is 
the old proverb more forcibly demonstrated than in the case of 
machinery, that " A stitch in time saves nine." The wearing 
parts of the engine are few, are easily reached and placed, 
and the engineer who waits until same accident hai)pens to 
announce that he has long neglected the proper inspection of 
the part which could, at the proper time, have been replaced at 
a trifling cost, is not worthy of being placed in charge of any 
machine more complicated than a wheel-barrow. The same 
principle will apply with equal force to machinery of every type. 
There is a proper time to replace worn parts and a time it is too 
late to replace them. 

HOW TO SET THE MAIN VALVE. 

The only exact and final setting of the valve is by means of 
the indicator. As the valves are permanently set and all adjust- 
ments made before the engine is shipped, it is not supposed that 



302 



HANDBOOK ON ENGINEERING. 



the engineer will have occasion to reset them. Should the neces- 
sity for setting the valves arise, however, the following method 
will be sufficiently accurate : Break joints and take off the throttle- 
valve. The steam ports in the bushing will then be seen through 
the steam connection S. (This opening is on the side in fact, but 
is here shown on the top for convenience.) Bring the high- 
pressure piston exactly to the top of its stroke by turning the 
shaft in the direction the engine runs. This may be ascertained 




b}^ either taking off the water relief valve and measuring through 
its port, or more conveniently, by bringing the middle of the key- 
way in the shaft exactly over the center of the shaft. The key- 
ways are jjlaned exactly with the cranks, so that the position of 
the key way is the position of the high-pressure piston. With 
this j^iston at the top of its stroke, the valve edge a a, should 
show about Jg of an inch port or lead, and be moving towards 
the right as you stand behind the engine. If out, it may be 
brought to position by screwing the valve-stem into or out of the 
valve which is tapped to receive it. Be sure and set the jam nut 
solid when through. 



HANDBOOK ON ENGINEERING. 303 

After a test of a compound engine has been completed with 
the indicator, and the valve has in this manner been accurately 
adjusted, marks are scored on the end of the rocker arm, at its 
junction with its supporting bracket, in order to show the extreme 
points of oscillation of the rocker arm. If, therefore, in starting 
up a new compound engine, the eccentric rod is too long or too 
short, these marks will not coincide when the engine is turned 
round by hand to examine this j^oint. The eccentric rod must 
then be adjusted with the nuts provided for that purpose, until 
the scored lines on the rocker arm will coincide exactly. When 
this rod has thus been proven correct, the engine should then be 
put by hand on the dead center, with the high-pressure piston at 
the top of its stroke. In order to prove this upright position of 
the high-pressure piston exactly, two lines are scored on the 
faced-off end of the crank-box head on the high-pressure side, to 
which marks the keyway in the main shaft must be brought 
exactly. Then remove the back head from the steam chest and 
measure the distance from the rear end of main valve to the end of 
the steam chest, while the engine is in this position. This 
distance measured will be found stamped with steel figures on 
the finished face of the steam chest, underneath the back head. 
If the valve has not been disturbed, the measurement thus taken 
will agree with the figures. If it has been disturbed, the valve 
must be adjusted to correspond with the measurement. 

ADJUSTHENT OF ECCENTRIC STRAP AND CONNECTING ROD. 

Before starting the engine for the first time, the eccentric strap 
must be taken off and both the strap and eccentric carefully 
cleaned and lubricated with clean oil. The eccentric rod is 
hollow and might contain dirt or other injurious matter, and 
should be examined and thoroughly cleaned before putting on the 
engine. There must be a sufficient number of liners between the 



304 HANDBOOK ON ENGINEERING. 

joints of the strap, so that when the bolt is pulled up hard and 
tight the eccentric strap will still be free to run without binding. 
After the bolt has been tightened, take hold of the strap and 
shake it back and forth to be sure that it is free. If it binds in 
the least, it is certain to heat or cut either itself or the eccentric 
or probably both. When the upper ball joint on eccentric rod 
becomes worn it should be adjusted to take up the lost motion 
promptly. 

As to the connecting rods, the lost motion should be simply 
taken up without binding. No possible good, but much harm, 
can come from too tight an adjustment. 

GENERAL INSTRUCTIONS FOR HOHE REPAIRING. 

How to put in new bushings and cut the oil holes and 
grooves* — When new bushings are shipped to fill repair orders, 
they are turned to gauge so as to fit tightly in their respective 
places. A very careful mechanic may, by the use of a wooden 
block and hammer, be able to drive in bushings properly. The 
much safer course, however, is to use a bolt which passes through 
the bushing, and a nut and washer ; by screwing up the nut and 
taking reasonable care, the bushing is thus drawn surely and 
gradually into place. After the bushing is in place, the oil 
grooves must then be cut into it with a half-round chisel and 
hammer. The oil-holes must then be drilled ; these latter should 
be large and free ; no harm can come from having them too large, 
but much trouble will result if they are too small. The oil should 
have very free access through these holes to the grooves. We 
have conducted a long series of experiments to determine what 
form or style of oil groove would produce the best lubrication, 
and consequently, the most satisfactory results in each bushing, 
and, therefore, urge that grooves be cut in new bushings in strict 
accordance with the grooves and oil holes as shown in the old 



HANDBOOK ON ENGINEERING. 305 

bushiug which has beeu removed. This course is safer and bet- 
ter than to try experiments of your own. 

How to rebabbitt connecting tods* — Connecting rods may be 
re-babbitted at home, if preferred. You should provide yourself 
with a plug, preferably of cast-iron, turned to the exact diameter 
of the shaft or crank-pin and squared accurately on the end. A 
perfectly true surface is then required on which to lay the rod, so 
that the plug will stand in its proper position, exactly square with 
the rod. The original length of the rod must be known, and will 
be furnished by us on application, by stating the number of your 
engine. The center of the plug must then be placed at the proper 
distance from the center of the eye of the connecting-rod pin, and 
the babbitt metal poured into place. Moistened fire-clay will be 
found very convenient for confining the molten babbitt metal 
within its proper limits. After cooling, the babbitt metal should 
be dressed with chisel and file. Bear in mind that heavy service 
is required of these connecting rods, and that the engines run at 
higher speeds than is possible in any other type of engine, hence, 
nothing but first-class babbitt metal, or "genuine" babbitt 
metal, as it is called in the trade, will answer the purpose. I 
would, however, advise that the brasses be sent to the shop to 
be re-babbitt, and that duplicates be kept on hand, if necessary. 

How to rebabbitt main bearing: shells* — This is a very diflfi- 
cult piece of work to do at home, and it is not recommended that 
you attempt it ; it cannot possibly be done accurately by any one 
without special appliances for the purpose. The lines of the bab- 
bitt, internally, when complete, must be exactly parallel with the 
outside lines of the shell, else the shaft cannot lie on its bearings 
with equal contact throughout the length of the shell. The lack 
of equal contact will cause the shaft to bind, and in all probabil- 
ity, the limited bearing surface will cause friction and heating. 
The only way in which main bearing shells can be properly re- 
babbitted at home, is to first provide yourself with what is called 

20 



30(3 HANDBOOK ON ENGINEERING. 

a "jig," which is simply a special device that holds the main 
bearing shell and the central plug in their relative positions, ex- 
actl}'^, while the babbitt metal is being poured. After cooling, 
the ends of the shell should be dressed and the oil-holes and 
grooves must be properly cut, exactly as they existed when the 
shell was new. A simple and more satisfactory method, would 
be for each owner of an engine to purchase an extra pair of main 
bearing shells ; in this way, while one pair of shells is in use in 
the engine, the other pair may be sent in for rebabbitting, with- 
out the loss of time, and at trifling cost. Use nothing but first- 
class " genuine " babbitt metal in the main bearing shells. 

How to repair worn or badly scored wrist-pins. — Instruc- 
tions on this point are very simple: Don't! If, on examina- 
tion, you find you have allowed the wrist-pins at the upper 
ends of the connecting rods to become worn, or even badly 
scored, it is recommended that, having bought a new pair 
of wa'ist-pins and rebabbitted the brasses, you immediately take 
out the old pins and throw them away. It is useless to attempt 
to repair worn wrist-pins. If you turn them down until they 
present a smooth exterior (as some have proudly announced they 
have done) the diameter of the pin is so reduced that it will not 
fit the brasses and the reduced bearing surface will soon destroy 
it. Or, if 3^ou attempt to use a badly scored wrist-pin in new 
brasses, it will cut them out so rapidly that it would be more 
economical in the end for you to buy new wrist-pins than to 
attempt to use the old ones. The service on the wrist-pin of any 
engine is extremely heavy. These pins are made with the best 
l^ossible care, using the best selected materials, and after machin- 
ing them they are ground in special machinery. The brasses are 
lined with the finest possible babbitt metal and should last a long- 
time under heavy duty if properly lubricated ; yet, the use of an 
improper oil in the crank-case — either volatile or gritty — nul- 
lifies all these i)recautions. Therefore, if you find on examina- 



HANDBOOK ON ENGINEERING. 



307 



tiou, that the wrist-pins in your engine have become badly worn 
or badly scored, I would urge you to throw them away and buy 
new ones. 




Where the inclosed form of governor is used, the governor 
case is to be filled completely full of good cylinder oil, or with 
James Dalzell & Son., Ltd., Crank-case oil. Use nothing else. 
A nipple is screwed into the face of the inner case and extends 
through the first flange of the wheel in a radial direction. This 
nipple is closed by a cap. Turn the engine around till this nipi^le 
is on top and fill the case entirely full through the opening. The 
joint at the outer rim of the case, also the joint on face of hub, is 
made with a paper gasket. The oil is prevented from escaping 
along the spindle of the eccentric and out past the eccentric by a 
leather packing ring fitting around the spindle and between the 



308 HANDBOOK ON ENGINEERING. 

eccentric and the face of the case. If, after service, this should 
leak oil when the engine stands still, you must pack it tighter by 
putting in a thicker packer-ring of leather, so it shall be held 
tightly in its place and prevent the passage of oil. Be careful in 
locating the governor case on the shaft, so that the average posi- 
tion of the eccentric rod shall be vertical and that its extreme 
positions shall be alike on each side of a vertical line drawn 
tln*oughthe center of eccentric. Be very careful as to the lubrica- 
tion of the eccentric strap at the start. After it runs for a few 
weeks and gets a good surface, it will require little attention 
beyond regular oiling. When you start the engine, be sure to 
put plenty of oil on the eccentric direct, by hand. 

The best means for lubricating the valve and pistons is an 
Automatic Sight Feed Lubricator, which is treated of elsewhere. 
It is manufactured in a variety of forms, many of which are very 
effective in their working. With a good cylinder oil, the number 
of drops per minute can be regulated so as to effect the greatest 
economy of oil and distribute it in such a way as to do the 
engine the greatest amount of good. Any other system of lubri- 
cating the cylinders is defective. It will not suffice to give the 
engine an hour's supply of oil at one dose and then allow it to run 
without any cylinder lubrication for the remainder of that hour. 
The construction of the AVestinghouse engine is such as to be 
favorable to the economy of oil in this direction, because the 
pistons moving up and down in a vertical direction do not have 
the same tendenc}^ to wear as in the case of a horizontal engine, 
where the heavy j^iston-head drags back and forth. These im- 
mense bearing surfaces, moreover, reduce the amount of pres- 
sure per square inch to a minimum. The Automatic Lubri- 
cator is to be attached to the steam-pipe, within easy reach of 
the engineer, so that it can be refilled without loss of time. 
Witii each hibrieatoi- is packed specific directions for starting 
and oi)eratiiig it, wliic^li should be followed carefully. Jt may 



HANDBOOK ON ENGINEERING. 309 

be well to note here that, in order to get the best results 
and avoid trouble, no other than a first-class cylinder oil 
should be used in the cylinders. Approximately, one pint of 
cylinder oil per day for every fifty horse-power, and pro- 
portional, will be required for engines, depending on the amount 
of work to be done. The lubricator furnished on each engine 
will serve as a partial index of the quantity of oil required. 
These cups are not intended to hold over 8 to 10 hours' supply 
in any case. Feed regularly and slowly. The use of Valvoline, 
or 600 W. Vacuum Cylinder Oil, made by the Vacuum Oil Co., 
Rochester, N. Y., is recommended, although there are others 
who make a first-class article. 

SOME POINTS ON CYLINDER LUBRICATION. 

**In the first place, use the best automatic feed cup that can 
be secured. Don't be satisfied with the old-fashioned direct 
feed, or a cheap automatic. A good cup will save many a hun- 
dred per cent on its cost in a year. Don't get the kind which, on 
account of its peculiarity of feed, is adapted for a light oil only ; 
you will then be shut out from using a" dark oil, which may 
be far more serviceable and economical in every respect. Get 
a cup where the drop of oil cuts off square and passes either 
down or up through a glass tube into the steam pipe. This 
kind will feed oil perfectly ; if yours is not this kind, it will 
pay you to change it." 

'^Take good care of your cup. Don't let it leak around 
the glass tubes or other joints, for if it does the water will escape 
as it condenses, and the oil will clog up the escape pipe and 
stop feeding. Use in it only the best grades of cylinder oil, 
made by large manufacturers of established reputation. Don't 
run in your cylinders any kind of poor stuff that may be offered, 
because it is cheap ; it is a dangerous experiment. Feed a good 



310 HANDBOOK ON ENGINEERING. 

oil sparingly — don't drench the cylinder. Too much oil is as 
bad as water in the cylinder. Engineers have been known to run 
a couple of quarts per day of cheap oil into an ordinary sized 
cyhnder, and thought they were doing just right ; this is positive 
abuse of an engine. In almost all cases where too much oil is fed , — 
cut it down. Two to four drops per minute on engines from 50 
to 150 H. P. are all that is necessary, if the oil is good. Just 
enough to do the work and no more, will afford best results. As 
long as the valve stem does not cause trouble, you may know the 
valves are working smoothly and that you are giving oil enough. 

AUTOMATIC LUBRICATORS. 

An Automatic Sight Feed Lubricator should be furnished 
with every engine, which enables the engineer to see the oil as it 
is fed drop by drop to the engine. The construction of these 
lubricators is such that the steam entering a chamber is condensed 
and this water of condensation finds its way into another com- 
IDartment of the lubricator, wherein is contained the oil to be fed 
to the engine. The drop of water, by reason of its greater spe- 
cific gravity, seeks the bottom of this oil comj^artment and forces 
out an equivalent bulk of gil into the steam pipe, whence it is 
carried by the current of steam into the cylinders and is distrib- 
uted upon the wearing surfaces intended to he lubricated. This 
method insures regularity and economy. 

There are numerous automatic lubricators made by various 
manufacturers throughout the country, many of which will per- 
form their functions successfully. I have used several of the 
best types, and consider any of them suitable for the purpose ; 
Jut herewith is submitted, with description of the cup I have 
been using for some years. 

This is the up-feed cup, showing an external view and sec- 
tional view of the same. Attachment is made to the steam-pipes 



HANDBOOK ON ENGINEERING. 



311 



at the points F and K. In operation, the condensing chamber F 
provides for the condensation of steam which enters at the pipe F. 
This water of condensation passes down through the valve D and 
through the tube P shown in the section and discharges into the 
bottom of the oil vessel ^1. This vessel is filled with oil when the 
cup is started, the height of oil being shown in the index glass J. 




THE ^'DETROIT" LUBKICATOR. 



The operation is as follows : The valve N being opened, the valve 
D is opened and the drop of water is allowed to pass from the 
condensing chamber F downward through the water tube and into 
the bottom of the oil chamber ^4, where it displaces a drop of oil 
of equal bulk on account of its greater gravity, and this drop of 
oil is forced out past the valve E^ making its appearance in the 
feed glass H^ as it starts on its way to the steam-pipe. It is 
carried by the current of steam to the engine and lubricates the 
valve and the pistons. When the oil cup is empty, the valve D 



312 



HANDBOOK ON ENGINEERING. 



is closed and the drain valve G is opened, which will allow the 
water in the oil chamber to be blown out pre[)aratory to the re- 
filling at the plug C. By opening the valves G and D, steam will 
be blown through the sight glass J, thereby clearing the same 
from any clogging up of the oil, which would disfigure it. The 
amount of oil to be fed by the lubricator will be regulated by the 
valve D, controlling the amount of water admitted, and the valve 
E controlling the discharge of the oil into the sight glass. The 
valve N is to be left wide open in operation and its object is to 
provide for the accidental breaking of the glass H. 




Sketch showing proper method of attaching cup to prevent the 

oil from dropping into the well, and not going into 

the cylinder. 



These cups should be attached to the steam pipe, in strict ac- 
cordance with the instructions contained in the box in which the 
lubricator is packed. The greatest enemy to proper performance 
is leakiness ; all joints must be absolutely tight, otherwise the 



HANDBOOK ON ENGINEERING. 313 

water of coiideiisatiou, instead of perforiuiug its duty of displac- 
ing the oil, will ooze out at the leaks and the cup will refuse to 
work. In most cases, provision is made for a column of water 
which may stand 12" or more in height and enable the cup to 
work more positively, by giving it a greater pressure in the dis- 
placement chamber, due to the height of the column. A suitable 
oil is essential to the proper working of such a lubricator, as well 
as to the proper lubricating of a steam-engine. An improper oil 
will not feed through the cup as it should, on account of its dis- 
position to disintegrate and go off in bubbles, when exposed to 
the heat of the steam. 

SETTING A PLAIN SLIDE VALVE WITH LINK flOTION. 

The setting' of a slide valve operated by a link motion does 
not differ materially in principle from the method pursued when 
setting the ordinary slide valve driven by one eccentric. A link 
motion may be considered as a means of driving a valve by two 
independent eccentrics, either of which controls the functions of 
the valve wholly or in part, according to the position of the link. 
Thus when the link is in either extreme position, the eccentric 
driving that end of the link in line with the link-block pin may be 
considered as being entirely in control of the valve action, and, 
vice versa, when the link occupies the other extreme position of 
its throw, as actuated by the reverse lever, the other eccentric 
becomes possessed of the controlling function. Practically, 
however, the operation of the link motion is very complicated and 
the movement of one eccentric materially modifies the action of 
the other. Since the interfering action is least at the extreme 
positions of the link and greatest in mid-gear, the plan is followed 
of setting the valve with the link in full gear both forward and 
backward motion, and, as before stated, the procedure is on the 
theory of independent action of the eccentrics. 



314 



HANDBOOK ON ENGINEERING. 



In the accompanying diagram, a link motion is shown driving 
a plain slide valve without the intervention of a rocker. Each 
eccentric is set with reference to the crank-pin, the same as it 
would be with a simple slide-valve engine. The eccentric A is 
set on the shaft with the same angular advance, QMO, as would 
be required for an ordinary engine to run in the direction indi- 
cated by the arrow. Now, since the crank pin is at C, if it were 
necessary to reverse the simple engine with one eccentric, it would 
be necessary to change the position of the eccentric so that instead 
of being ahead of the bottom quarter line QM, it would be ahead 




rj*_iLINW HANGER 



of the top quarter line F3I by an amount of angular advance made 
necessary by the lap and lead of the valve. Therefore, the eccen- 
tric would come in the position of the eccentric A^, or with its 
center line coinciding with MJSf, giving it the angular advance 
PMN. Now it should be clear that if an engine is to be equipped 
with two eccentrics, so that it may run with equal facility in 
either direction, they will occupy the positions A and A^. We 
will suppose that an engine having a link motion is to be over- 
hauled and the valve motion to be properly set. This will mean 
that the eccentrics will be properly located for the correct angular 
advance, and that the eccentric rods will be adjusted to the right 
length. When these conditions are obtained, the valve should 



HANDBOOK ON ENGINEERING. 315 

perform its functions properly iu both forward and backvvaixl 
motions, and also when the link is " hooked up." 

Before starting to set the valve, it is best to take a general 
survey of the valve motion parts and see if the eccentrics are 
somewhere near the proper location on the shaft relative to the 
crank-pin. If they are obviously much out of position, they 
should be shifted and adjusted as near the correct position as 
possible by the eye ; doing this at the beginning will often save 
confusion and much time. The dead centers will be found by the 
method given on page 228. The operation should be carefully 
performed, as upon it depends the success of the work. After 
having found the dead centers and having them marked so that no 
mistake will occur when " catching " them with the tram, the 
valve positions may be taken for the four positions , that is, front 
and back centers in forward motion, and the front and back 
centers in backward motion. Put the reverse lever in full gear in 
one motion or the other, whichever is' most convenient, and turn 
the fly-wheel in the direction the engine would run for the given 
reverse lever position. Suppose the link stands in the position 
shown in the diagram, the fly-wheel should be turned in the direc- 
tion indicated by the arrow until the dead center is reached, 
which is known when the tram drops into the prick mark. The 
position of the valve is then noted and a measurement taken. If 
the valve shows the steam port open, measure the distance with a 
steel scale, or it may be done by sharpening a stick wedge-shaped 
and shoving it into the opening. By noting the depth to which 
it goes at the valve face the opening can be readily measured on 
the removal of the wedge. We will suppose the distance is found 
to be I". The measurement should be set on a sheet of paper 
laid out as follows : — 

FORWARD MOTION. BACKWARD MOTION. 

Front center, Front center, 

Back center. Back center, #" lead. 



316 HANDBOOK ON ENGINEERING. 

It will be seeu that the valve opening is set down as being 
J" lead, and as being on the back center in the backward motion. 
After having verified the measurement taken, the engine can be 
" turned over " in the same direction as before until the opposite 
dead center is caught by the tram. It may be found that the 
valve does not show open in this position but covers the steam 
I^ort. To find the position of the valve edge relative to the steam 
port, scribe a line in the valve seat face along the edge of the 
valve and then turn the fly-wheel until the valve uncovers the 
steam port. The distance the valve laps over when the crank is 
on this dead center ca?i then be readily measured. Suppose the 
distance is found to be A". It is set down on the log as 
follows : — 

FORWARD 3I0TI0N. . BACKWARD MOTION. 

Front center. Front center, i" blind. 

Back center. Back center, |" lead. 

The valve position is put down as being i" blind, which is the 
same as saying that it has i" negative lead, and is fully as com- 
prehensive as the latter term. The reverse lever should now be 
thrown into the opposite gear and the measurements taken for 
both front and back centers the same as has been described for 
the backward motion. It may now be supposed that when all the 
measurements have been taken the log reads as follows : — 

FORWARD MOTION. BACKWARD MOTION. 

Front center, J" blind. Front center, i" blind. 

Back center, -f-^" lead. Back center, |" lead. 

When in forward motion, the valve is open -f-^" on the back 
center and lacks i" of being open when the crank is on the front 
center. The total lead due to the angular position of the 
eccentric is -f^" minus J" = Jg-". One-half the total lead should 
be given to each edge of the valve so that it will be necessary to 
lengthen the eccentric rod JBi, Jg" + i" = ^9_" to get the valve 



HANDBOOK ON ENGINEERING. 317 

into its proper position. A little reflection will show the reason 
for lengthening the eccentric rod B^. In speaking of the front 
and back centers, they are taken to coincide with the crank and 
head ends of the cylinder. When the piston is at the crank end 
of the cylinder, the crank is on the front center. By referring to 
the log it will be seen that to adjnst the backward eccentric rod 
B, it will also be necessary to lengthen it. The valve is i" blind 
on the front center and has | " lead on the back center. The 
total lead is, therefore, |" minus J" = J". One-half i"==i", 
which being added to the amount the valve is lapped on the front 
center, makes i", or the amount the eccentric rod B will have to 
be lengthened to make the valve open equally at each end of the 
piston stroke. The opening the valve has when the crank is on 
the centers is called the lead and in the case of the backward 
motion, it is found that after the eccentric rod is lengthened, the 
lead is i", which is too much for most cases and in this one we 
can assume that gV" would be about right. 

Before explaining the adjustment of the eccentric for the cor- 
rect angular advance, it will be in order to call attention to the 
necessity of making the adjustment for the eccentric rod lengths 
first. The eccentric rods are lengthened or shortened, as the 
case may require, by inserting or removing liners between the 
eccentric rods and straps at B. Other forms of construction 
provide different means for adjustment, but the principle is the 
same in each. It will be noted that the correct length for the 
two motions is obtained by adjusting the eccentric rod corre- 
sponding to that motion. Any attempt to correct an irregularity 
by changing the length of the valve rod F will result erroneously, 
unless both eccentric rods require the same amount of movement 
and in the same direction. After having adjusted the eccentric 
rods to the correct lengths, the angular advance of the eccentric 
A can be changed. Place the crank on a dead center and have 
the reverse lever thrown in the backward motion and then 



318 HANDBOOK ON ENGINEERING. 

loosen the set screws that hold the eccentric to the shaft and turn 
it towards the crank until the valve shows open -^^"^ and then 
tighten the set screws on the shaft. After all the adjustments 
have been effected, it is always advisable to turn the engine over 
again and catch all the dead centers, so that the correctness of 
the adjustments can be verified. After taking the new log, it 
will usually be found that some slight irregularities have been 
introduced, especially if any of the adjustments have been consid- 
erable, as the changes made for one motion will affect the other 
slightly. 

The link motion shown in the cut is so connected that the lead 
increases as the link is shifted towards the center. If the eccen- 
tric rods be oppositely connected to the link, the engine will run 
in an opposite direction for a given reverse lever position and the 
lead will decrease as the lever is shifted towards the center. The 
link motion for hoisting engines is quite commonly connected in 
this manner, for the reason that the engine will stop when the 
lever is put on the center, which is not the case when connected 
as shown. Of course, in such a case, the admission and cut-off 
take place at the same position in the stroke and the compression 
is high, but with a light load the engine will run on the center, 
which is considered objectionable in the case of the hoisting 
engine. 

VALVE=SETTINQ FOR ENGINEERS. 

Plain slide- valve* — The plain slide-valve, while the simplest 
valve made, is perplexing to one who has not made a study 
of it. Unless one understands the principles of the valve 
and its connections, he will probably meet with trouble when he 
attempts to set it. We will first place the engine (see p. 228) 
on the dead center, and will simply explain the other steps 
that have to be taken. In the first place, it should be understood 
what result is obtained by adjusting the position of the eccentric 



HANDBOOK ON ENGINEERING. 319 

and the length of the valve stem. The position of the eccentric, 
when the valve is set, depends upon which way the engine is to 
run and whether the valve is connected directly to the eccentric 
or whether it receives its motion through a rocker which reverses 
the motion of the eccentric. When the valve is direct connected, 
the eccentric will be ahead of the crank by an amount equal to 90°, 
plus a small angle called the angular advance. When a reversing 
rocker is used, the eccentric will be diametrically opposite this 
position, or it will have to be moved around 180° and will follow 
instead of lead the crank. Shifting the eccentric ahead has the 
effect of making all the events of the stroke come earlier, and 
moving it backwards has the effect of retarding all the events. 
Lengthening or shortening the valve stem cannot hasten or retard 
the action of the valve, and its only effect is to make the lead or 
cut-off, as the case may be, greater on one end than on the other. 
The general practice is to set a slide-valve so that it will 
have equal lead. The lead is the amount that the valve 
is open when the engine is on the center. To set the valve, 
therefore, put the engine on the center, remove the steam-chest 
cover so as to bring the valve into view, and adjust the eccentric 
to about the right position to make the engine turn in the direction 
desired. Now make the length of the valve-spindle such that the 
valve will have the requisite amount of lead, say -^^ of an inch, 
the amount, however, depending upon the size and speed of 
the engine. Turn the engine over to the other center and measure 
the lead at the end. If the lead does not measure the same as 
before, correct half the difference by changing the length of the 
valve-stem, and half by shifting the eccentric. Suppose, for 
example, that the lead proved to be too great on the head end by 
half an inch. Lengthening the valve-stem by half of this, or J 
inch, would still leave the lead J inch too much on the crank 
end. That is to say, the valve would then open too soon at both 
head and crank ends, and to correct this, the eccentric would 



320 HANDBOOK ON ENGINEERING. 

have to be moved back far enough to take up the other quarter- 
iuch. Sometimes it is not convenient to turn the engine over by 
hand, in which case the valve may be set for equal lead as fol- 
lows : To obtain the correct length of the valve-stem, loosen the 
eccentric and turn it into each extreme position, measuring the 
total amount that the valve is open to the steam ports in each 
case. Make the port opening equal for each end by changing the 
strength of the valve-stem. This process will make the valve- 
stem length as it should be. Now put the engine on a center and 
move the eccentric around until the valve has the correct lead and 
fasten the eccentric in that position. This will determine the 
angular advance of the eccentric. 

The plain slide valve* — The function of the slide-valve is 
to admit steam to the piston at such times when its force can be 
usefully expended in propelling it, and to release it when its pres- 
sure in the cylinder is no longer required. Notwithstanding its 
extreme simplicity as a piece of mechanism, no part of the engine 
is more puzzling to the average engineer when the problem to be 
solved is to determine beforehand the results which will be pro- 
duced by a given construction and adjustment, or the proportions 
and adjustment required to produce given results. All who have 
had any experience in constructing and setting slide-valves are 
aware, in a general way, that the events of the stroke cannot 
be independently adjusted ; for instance, a cut-off earlier than 
about I of the stroke. 

To set a slide valve* — The valve should be set in such a man- 
ner that when the engine is on the dead center, the part admitting 
the steam to the cylinder is open a small amount, as shown in Fig. 1, 
which is called lead. The object of lead is to enable the steam 
to act as a cushion against the i^iston before it arrives at the end 
of the stroke, to cause it to reverse its motion easily, and also to 
supply steam of full pressure to the piston the instant it has passed 
dead center. Tlie lead required varies in different engines from 



HANDBOOK ON ENGINEERING. 



321 



BIT ^^ TB without regard to size or kind. Fig. 1 also shows the 
position of eccentric, which should always be set ahead of the 

/IT POINT OF T/\KING STEAM. 




Fio-. 1. 



crank at an angle of 90°, plus another angle called Ihe •' angular 
advance." When the valve is to have lead the angular advance 
must be a little greater than when no lead is desired. 




Fig. 2. 

Fig* 2 shows the position of eccentric at point of cut-off ; also 
position of Piston. 



POSJTION WHEN COMPfiESSION BEGINS. 




Fig. 3. 

Figf. 3 shows position of valve when compression begins. It 
also shows position of eccentric. The compression at the left 

21 



322 



HANDBOOK ON ENGINEERING. 



end, towards which the piston is moving, has just commenced, 
and the exhaust is about to take place from the other end. 

/IT POINT OF TAKING STEAM. 




Fiff. 4. 



Fig* 4 shows the position of eccentric and valve in an engine 
with a rocker-arm. 



AT POINT or CVT-OFfT 




Fig. 5. 

Fig-* 5 shows the position of valve and eccentric at point of 
cut-off. 

^^m f'O^T/ON WHEN COMPRESSION BEGINS. 




Fig. e>. 
Fif* 6 Bhows point oi compression. 



HANDBOOK ON ENGINEERING. 323 



CHAPTER XIII. 

TAKING CHARGE OF A STEAH POWER PLANT. 

It is frequently the case that an engineer, on assuming charge 
of a steam power plant, proceeds as though he were thoroughly 
familiar with the condition of the engine, boiler and entire sur- 
roundings. He plunges headlong into his duties, without first 
taking his bearings. A skillful physician on taking a case, would 
not proceed in this manner ; neither would a lawyer. The physi- 
cian would feel the patient's pulse, look at his tongue, take his 
temperature, observe his color and ask a number of questions, all 
for the purpose of enabling him to make a correct diagnosis of 
the patient's ailment. The first duty of an engineer, when he 
takes charge of a plant, is to ascertain the arrangement and con- 
dition of the plant. Since the boiler is the most important mem- 
ber of the plant, it should be the first to engross his attention, and 
it, together with its connections, should be examined as closely as 
time and surrounding conditions will permit. He should look the 
boiler all over, internallj^ and externallj^ if possible, in view of 



324 HANDBOOK ON ENGINEERING 

mud, scale, grooving, pitting and defective braces. The furnace 
should be examined next, in view of burnt-out brickwork, grate 
bars and door linings. It may be that the furnace has distorted 
or cramped proportions, or it may be too large. The ])i'idge wall 
may be so constructed as to huddle the llames in one spot on the 
fire sheets of the boiler ; or it may be of such shape and in such 
condition as to cause the ignited gases to become dissipated in 
the combustion chamber. Even the combustion chamber itself 
may require the service of a bricklayer. He should next examine 
the safety valve and see that it is of ample capacity to relieve the 
boiler of surplus steam, and that it is in thorough working order. 
The first duty of an engineer when entering his plant at any 
time, is to ascertain how the water in the boiler stands, or, 
in other words, just how much water the boiler contains. He 
should open the gauge cocks first and note what comes from each 
in turn ; then open the cocks or valves connecting the glass gauge 
and note the water line there shown. He should also blow the 
water column out, in case any sediment may have choked any of 
the passages, which would be liable to give a false impression as 
to the actual quantity of water contained in the boiler. Should 
the water be found at tho correct height, he may now proceed to 
get up steam ; open the damper, pull down the banked fire and 
spread it evenly over the grate, adding a quantity of green fuel. 
Allow the steam to rise slowly ; do not force it. This applies 
especially to raising steam in a boiler which has been cold, as the 
expansion of the parts of the boiler due to the heat should take 
place slowly and evenly; otherwise, the life of the boiler will be 
shortened. While waiting for the steam to come up to the desired 
point, the engineer should now get his engine ready for the day's 
run. Fill all the oil cups and cylinder lubricator, so as to be 
ready to operate as the engine starts. With a hand oil squirt 
can, go around all the small brasses, connections, etc., and, in a 
word, well lubricate all the parts where fiiction takes place. 11 



IIANDHOOK ON KN(; INKI'JMNO . .r/i) 

you liuve mu oil |Himp Cor your cyliudcr and valves, it would he 
well to inject a small quantity of cylinder oil before the engine is 
started, while the stop-valve is open, during the time the engine is 
being ^ warmed up." After the engine cylinder is warmed 
through, the fire should again be looked at, and dealt with 
according to the indications. Of course, the water gauge glass 
must be looked at frequently, not only while raising steam in the 
morning, but at all times wliile the boiler is in operation. 

Everything being in readiness, the engine is started slowly at 
first, the speed being gradually increased until the limit is reached. 
The day's run is now fairly commenced. A boiler should be 
blown down one gauge every morning before starting the day's 
run to get rid of the mud, scale or anything that is held in 
mechanical suspension in the water. Before starting in the 
morning and at noon is the best time to do this, as the sediment 
has settled to the bottom during the night, after the circulation 
of the water has stopped. When blowing a boiler down, always 
remember to open the blow- valve slowly — be careful not to blow 
too long, and then to close the valve slowly. 

An engineer or attendant cannot be too careful in handhng 
the many appliances with which a steam plant is equipped. The 
principal things to which an engineer should give his attention 
during the operation of his boiler day by day are, as follows : 
The maintenance of the water at the proper level, as near as pos- 
sible, and avoiding fluctuations in the pressure of steam. See 
that the firing is done correctly and economically so as to obtain 
from every pound of coal all that is possible under the con- 
ditions existing. The raising of the safety valve from its seat, 
at least once daily ; the blowing out of the water column twice 
daily, or oftener, if the water used is very dirty ; the frequent 
opening of the water gauge cocks, or try cocks, as they are 
sometimes called, and not depending entirely on the gauge glass 
for the correct height of water ; the blowing down of the boiler 



32() HANDBOOK ON ENGINEERING. 

one gauge every day; the keeping of all valves, cocks, fittings, 
steam and water-tight, clean and in good working order. 

When shutting down the plant for the night, the fires should 
be cleaned out and the live coals shoved back on the grates and 
banked ; that is, green coal should be thrown upon them, suffi- 
ciently thick to cover all the glowing fuel. Pump in the water 
until it reaches the top of the glass gauge. This should be done 
to insure a sufficient quantity from which to blow down in the morn- 
iug, and also to allow for any small leaks. Then close the cocks or 
valves connecting the glass gauge. Should this glass break dur- 
ing the night and the valves be left open, there would not be much 
water to start with in the morning. Leave the damper open a 
little, just sufficient to allow the gases which will rise from the 
banked fires to escape up the chimney. Finally, make sure that 
all the valves about the plant which should be closed, are closed ; 
and all those which should be left open, are open. Of course, 
the foregoing is applicable to a plant where there is no night 
engineer. But in any case, no matter how many assistants an 
engineer may have under his control, he should be familiar with 
all details of the plant under his charge. 

One of the most important points in connection with the opera- 
tion of a steam boiler, is the preventing of corrosion, both 
internally and externally. One of the best aids to secure the 
well working and longevity of the steam boiler, or, in fact, the 
whole plant, is by being regular and punctual in a certain course 
of treatment, which has been proven to be effectual and beneficial 
in its results. All conditions do not require the same methods of 
treatment; therefore, it is absolutely necessary that the engineer 
in charge familiarize himself with all the conditions under which 
his plant is running, for then, and then only, can he intelligently 
prescribe and act accordingly. Above all, let him remember 
the adage, " Eternal vigilance is the price of safety," especially 
where a steam boiler is concerned. 



HANDBOOK ON ENGINEERING. 327 

ECONOMY IN STEAM PLANTS. 

In these days of close figuring upon expense in office buildings 
and manufacturing plants, what may at first appear insignificant 
items may actually make all the difference between a good margin 
of profit and an actual loss. 

The fuel expense is one of the largest in the operation of the 
majority of plants, and any reduction which can be made in the 
amount of fuel used, while maintaining the same amount of power, 
is considered a direct gain. The evaporation of more than nine 
pounds of water per pound of coal, is looked upon with suspicion 
by many, as it is not thought possible to obtain more than this 
amount in even the best designed and well regulated furnaces and 
boilers, especially when the firing is done by hand. The actual 
value of the fuel depends upon the way in which it is used, fully 
as much as on any other factor. The heat unit in the coal should 
be as much as possible utilized, as in one pound of good steam 
coal there is about 14,000 B. T. U., and about 10,000 of this 
amount can be utilized, so that 4,000 heat units are lost. The 
mixture of gases in a furnace depends upon the amount of air 
used. One pound of coal requires, theoretically, about Iwelve 
pounds of air to burn completely. But, in practice, about twice 
this amount is required in the present boiler furnace. To have 
good combustion coal requires a good draft. The gases are con- 
sumed near the fire, and the waste gases carry the heat to the 
boiler on their way to the stack. The boiler ought to have suffi- 
cient heating surface, or the hot wasted gases ought to travel a 
sufficient distance to be cooled down to about 350 degrees Fah- 
renheit ; which temperature is found high enough to produce a 
good draft in a stack of, at least, 100 feet high. 

How a bad draft will unnecessarily increase the coal bill, is 
this: That of all the fuel burnt to perform certain work, ascer- 
tained proportion is consumed to keep the heat of the furnace up 



o2.S HANDBOOK ON ENGINEEKING. 

to stiy, 212 degiL'us Falir., without miikiug tmy stcum whiituver 
which is available for work. This quantity varies from 20 to 30 
per cent, according to conditions, which are affected by various 
causes, such as leakages of steam, air, or water. Now, the only 
available power for work which we get from our fuel is the margin 
between this, say thirty per cent required for the said purpose, 
and what we generate above that. An engineer should notice the 
general condition of his boiler or boilers, aud the equipments of 
same ; he should examine the boiler both inside and outside, 
ascertain the dimension of grates, heating surfaces, and all im- 
portant parts. The area of heating surfaces is to be computed 
from the outside diameter of water-tubes, and the inside diameter 
of fire-tubes. All the surfaces below the main water level which 
have water on one side and products of combustion on the other, 
are to be considered as water-heating surfaces. If he finds that 
the boiler does not come up to what he thinks it should, he should 
put the boiler and all its appurtenances in first-class condition. 
Clean the heating surfaces inside and outside of boiler, remove 
all scale from flues and inside of boiler ; remove all soot 
from inside of flues, all ashes from the flame-bed or com- 
bustion chamber, and all ashes from smoke connections. Close 
all air leaks in the masonry and poorly fitted cleaning door. 
See that the damper in britching or smoking-flue will open wide 
and close tight. Test for air leaks through the crevices, by 
passing the flame of a candle over cracks in the brick work. A 
good, attentive fireman, who understands his business and will 
keep his bars properly covered without choking his fires, is really 
worth double the wages of an ignorant or inattentive one, as his 
coal bills would certainly prove. All an engineer can do is to 
keep the steam piston and valve or valves tight. Also the drains 
from his engine, and all drains on steam traps in the plant tight ; 
also, his engine cleaned and well-oiled, and not keyed np too tight. 
If in a heating plant, he should see that the back pressure valve is 



[lANDHOOK ON KN(;iNEF.KlX( 



o20 



at all times tight, as it docs not take niueli oi a leak tu show a 
difference in his coal bill at the end of a month. He should keep 
all valves in the pumps in his plant tight, and see that the pump 
piston is packed, but not too tight. After a pump 4s packed, you 
should be able to move it back and forth by hand ; if the pump 
valves leak he can take them out and smooth them up with sand- 
paper. He should see that the feed-water to the boiler is at least 
208 degrees Fahrenheit : if it is under 204 degrees, his heater is not 
right, as the poorest heater will heat the feed-water to 204 ; it 
would be well to overhaul the heater — it may be full of scale ; or, 
if an open heater, the spray may be off. In most first-class 
plants, the feed-water is 212 Fahrenheit. 

PRIMING. 

The term priming is understood by engineers to mean the 
passage of water from the boiler to the steam cylinder, in the 
shape of spray, instead of vapor. It may go on unseen, but it is 
generally made manifest by the white appearance of the steam as 
it issues from the exhaust-pipe as moist steam, Avhich has a white 
appearance and descends in the shape of mist, while dry steam 
has a J^luish color and floats away in the atmosphere. Priming 
also makes itself known by a clicking in the cylinder, which is 
caused by the piston striking the water against the cylinder head 
at each end of the stroke. Priming is generally induced by a 
want of sufficient ateam-room in the boiler, the water being car- 
ried too high, or the steam-pipe being too small for the cylinder, 
which would cause the steam in the boiler to rush out so rapidly 
that, every time the valve opened, it would induce a disturbance 
and cause the water to rush over into the cylinder with the steam. 

CONDENSING ENGINES. 

It has been explained that the atmosphere exerts a pressure 
of about 15 lbs. per square inch on all surfaces with which it 



)^30 HANDBOOK ON ENGINEERING. 

is in contact. Tiie atmospliere is in contact with one side of 
an engine piston when the exhaust is open, and, consequently, 
the steam in pushing the piston forward, has to overcome this 
atmospheric pressure of 15 lbs. per square inch. The useful 
pressure of steam is, therefore, whatever pressure there is 
above the pressure of the atmosphere, and this is the pressure 
that the steam gauge shows. When the gauge says 60 lbs. we 
really have 75 lbs., but 15 lbs. of it does not count, because it 
is balanced by the atmospheric pressure on the other side of 
the piston. If we had sixty-pound steam pressing on the pis- 
ton and could get rid of the atmospheric pressure on the side 
of the piston, the steam would exert a force of 75 lbs. per square 
inch, a very respectable gain, indeed. We might remove the air 
pressure by pumping it out, but the amount of power required in 
doing the i)umping would be equal precisely to all gain hoped for, 
plus the friction of the pump ; therefore, there would be an 
actual loss in the operation. But there is another way of remov- 
ing the air pressure. It has been explained that a cubic inch of 
water vaporizes and expands into a cubic foot of steam at atmos- 
pheric pressure. If, after getting this cubic foot of steam, we 
take the heat out of it, we again turn it into the cubic inch of 
water. Assume the engine cylinder to hold just a cubic foot of 
steam, and assume that the stroke is complete and ready for the 
exhaust valve to open and permit this foot of steam to escape, 
and assume that this cubic foot of steam has expanded 
down to atmospheric pressure, that is, 15 lbs., absolute i^ressure. 
Now, instead of opening the cylinder to the atmosphere, we dose 
the cylinder with cold water. The heat leaves the steam and 
goes into the water and the steam turns to water, leaving in the 
cylinder the condensed steam in the form of a cubic inch of 
water. The steam formerly filled the cylinder, and now it fills 
but a cubic inch of it, consequently, we have produced in the 
cylinder a vacuum which has the effect of adding about 15 lbs. 



HANDBOOK ON ENGINEERING. 3ol 

per square inch, to the force of the steam on the other side of the 
piston, by virtue of removing that much resistance to its forward 
motion. The heat which was in the steam has gone into the con- 
densing water, except the trifle that remains in the cubic inch of 
condensed water. We must get this condensed water out of the 
cylinder, and it will be an advantage to pump it })ack into the 
boiler, for it is pure and it is hot. 

This is the general principle of the condensing engine. It 
gives us the grand advantage of a heavy increase in the useful 
pressure acting to push the piston forward ; it gives us pure 
water for use in the boiler, and it saves in the feed-water the 
heat that would otherwise go out of the exhaust pipe. But it is 
not practicable to condense the steam in the cylinder by dosing 
the cylinder with cold water. In practice, the steam is allowed 
to go into a separate condensing vessel, called the condenser. 
The condenser is precisely the opposite of the boiler. The boiler 
is the machine for putting heat into the steam to vaporize it, and 
the condenser is the machine for taking heat out of the steam and 
turning it into water again. In the condensing engine, one of 
these machines is pushing on the piston and the other machine is 
pulling on the piston. The gain by condensing is so great that 
it is a profitable piece of business to apply a condenser to any 
large non-condensing engine. The condenser requires a pump to 
withdraw the water of condensation, and this pump must be in 
reality an air-pump. In practice, they employ an air-pump and 
condenser combined in one structure, separate from the engine, 
and driven either by rod connection from the engine, or by a belt 
from the engine, or by an independent steam pump. The arrange- 
ment will depend much upon the situation. The belt-driven pump 
permits of the condenser being set in any convenient position 
independent of the engine. 



lIANDI'.OOIv ON KNMJINFJORING. 



HIGH PRESSURK STEAM. 



It is generally believed that high-pressure steam is cheaper to 
use and costs but little more to generate than low pressure steam. 
A study of a table of the properties of saturated steam, to be 
found on another page in this book, will show wh}^ high-pressure 
steam is economical to generate, and a few calculations will 
prove instructive by showing what may be excepted from its use. 
To generate one pound of steam at 25 lbs. pressure, absolute, 
requires an expenditure of 1,155 thermal units, and to generate 
steam at 200 lbs. pressure, absolute, requires 1,198 thermal units, 
or an increase of only 43 thermal units for an increase of 175 lbs. 
pressure. Further investigation show^s that the temperature of 
steam at 25 lbs. pressure is 240° and at 200 lbs. jDressure, 382°, 
the difference, 142, being the number of degrees that the tem- 
perature of steam is raised with an expenditure of 43 thermal 
units. To put it in another way, the temperature of the steam 
has been raised nearly 60 per cent, with an increase of less 
than 4 per cent in the number of thermal units. It is con- 
venient to consider that the generation of steam takes place 
by two different stej^s, one of which is raising the water from 
32° to the temperature corresponding to the pressure of the 
steam, and the other is giving off the steam at this pressure, 
which process absorbs a quantity of heat that becomes latent 
or non-sensible. At 25 lbs. pressure, the sensible heat 
required to raise one II). of water from 32° to 240° is 
209 units, and to raise it from 32° to 382 degrees, the 
temperature of steam at 200 lbs. pressure requires 355 thermal 
units. The increase in the sensil)le heat of the water, there- 
fore, is 355 minus 200 =:- 140 units, or about the same as the tein- 
l^erature increase for these two pressures, which is 142'^. It is thus 
clear that the total increase in the number of heat units in steam 
raised from 25 lbs. to 200 lbs. ]n'essure is small (43° ns found 



HANDBOOK ON ENGINEERING. 333 

above) because the latent beat absorbed in the formation of the 
steam decreases as the pressure increases. It requires less heat 
to generate steam from water raised to o82° at 200 lbs. pressure, 
than from water previously raised to 240° at 25 lbs. pressure. 
To generate higher pressure steam, therefore, we must first 
apply enough heat to bring the water to a temperature 
corresponding to the higher pressure. This heat will be 
nearly proportionate to the increase in temperature. Then 
enough heat must be applied to the water to generate the steam, 
the amount of heat required for this purpose decreasing as the 
pressure increases. The combined result of these two processes 
is that it takes only a very small increase in the total heat to pro- 
duce the higher pressure steam. The idea may be suggested that 
if this higher pressure is obtained at the cost of so small an expen- 
diture of heat, it would not be reasonable to expect a large gain 
in economy from it, since it is not possible for the steam to do a 
greater amount of work than the equivalent of the heat which it 
contains. This would be true were it not for the fact that the 
larger part of the heat in the steam is rejected during the ex- 
haust. To illustrate, suppose an engine to exhaust at atmos- 
pheric pressure, or at about 15 lbs., absolute, and that the steam 
is saturated. As may be determined from the steam tables, there 
would be ejected 1,147 heat units per pound of steam, or 51 
heat units less than were found to be in a pound of steam at 
200 lbs. pressure. That is to say, under the above assumption, 
there are available only 51 heat units per pound of steam to do 
the work in the engine cylinder when the steam pressure is 200 
lbs. But we also found that the increase in the heat units in 
raising the steam pressure from 25 to 200 lbs. was 43, and hence 
the increase in proportion to the number available is large, 
although the increase in proportion to the total number required 



334 HANDBOOK ON ENGINEERING. 

to generate the steam is small. This shows why high-pressure 
steam is economical to generate and profitable to use. It should 
be stated that the only way in which the full benefit can be de- 
rived from high pressure-steam is by using the steam expansively, 
keeping the terminal pressure at release as low as possible. I 
will not take the space to give the calculations to prove this, 
but will compare a few results of calculations. Suppose steam 
to be used in a theoretically perfect engine at the pressure 
of 25 lbs., 50 lbs., 100 lbs. and 200 lbs. We will assume that 
in each case the cut-off is at one-third stroke, giving three 
expansions and a terminal pressure of one-third the initial pres- 
sure. The steam consumptions will then be, respectively, about 
16i, 16, 15 J, and 14 lbs. per horse-power, showing that gain 
from the increase in pressure is very slight. On the other hand, 
suppose the expansions to be carried to the atmospheric pressure 
in each case. The consumptions will then be about 27, 15, 11 
and 8 lbs. respectively, showing a marked decrease. 

Still another point should be mentioned in relation to the 
relative gain that is to be expected with the increase in pressure. 
Comparing the last figure, it will be observed that the decrease 
in consumption when the pressure increased from 25 to 50 lbs* 
was 27 minus 15 = 12 lbs., or 44 per cent. Again, when 
the jjressure doubled from 50 to 100 lbs., the consumption 
decreased only 4 lbs., or 27 per cent; and when the pressure was 
again doubled to 200 lbs., the consumption only decreased 3 lbs., 
or about 27 per cent. It is evident from this that the saving 
from an increase in steam j^ressure grows less as the pressure 
increases, and this is found to be the case in actual practice. 
There is another reason for this, also, coming from the losses 
incident to cylinder condensation and re-evaporation, which is 
more marked where there is a wide range in pressures than where 
the pressures are more uniform throughout the stroke. It is found 
that where the steam pressure is much above 100 lbs. gauge pres- 



HANDBOOK ON ENGINEERING. 335 

sure, no gain will result from a further increase in pressure with- 
out compounding, the advantage of the compound engine being 
that the extremes of temperature in the cylinders are not so great 
as with a simple engine. 

USING STEAH FULL STROKE. 

The steam engine is nothing in the world but an enlargement 
upon the end of the steam pipe, containing a piston against 
which the steam in the boiler may press. The piston moves a 
certain distance, and then the steam is allowed to press upon its 
other side, while the steam on the first side is allowed to flow into 
the atmosphere and go to waste. The slide-valve is the device or- 
dinarily employed to admit the steam, alternately , to opposite sides 
of the piston, and to permit the free outflow of steam from the 
reverse side of the piston. As the steam presses upon the piston 
the piston moves forward with a force equal to the pressure of 
steam per square inch, multiplied by the number of square inches 
of piston surface. Steam occupies the entire space from the sur- 
face of the water in the boiler, to the piston of the engine. The 
steam space, therefore, includes the steam space of the boiler, the 
steam pipe, the steam chest, and the cylinder space upon one side 
of the piston. As the piston moves, the entire steam space be- 
comes a little larger, by reason of the cylinder space becoming 
longer. Thus it will be seen that all of the steam in the boiler 
and pipe and engine, would expand a trifle and the pressure 
become somewhat reduced, were it not for the fact that new 
steam is made by the fire as fast as the piston moves forward. 
By this means the steam is maintained at about uniform pressure. 
It will be seen that the j)ressure is produced upon the piston 
by the generation of new steam from the water, that is, the fire 
causes the water to generate a quantity of steam, and this quantity 
of steam forces its way into the other steam, exerting a force 
upon the whole body of steam and pushing the piston ahead. 



336 HANDBOOK OX ENGINEERING. 

If au engine piston has a surface of 100 square inches and 
a stroke of ten inches, it follows that the piston will yield a 
thousand cubic inches additional steam space b}'^ its movement 
during one stroke, and consequently, the fire will be called upon 
to produce 1,000 cubic inches of new steam for each single stroke 
of the engine. If the pressure of the steam be eighty pounds to 
the square inch, the engine jMston will move with the force of 
8,000 pounds. When the engine has completed one stroke, we 
find an amount of power exerted equal to 8,000 pounds moved 
ten inches, and we then open the exhaust valve and empty into 
the atmosphere 1,000 cubic inches of eighty-pound steam. We 
keep on doing this for each stroke. Now your attention is par- 
ticularly called to the fact that when we empty the steam out of 
the cylinder, it is just as good as when it went into the cylinder; 
that is, it was 1,000 cubic inches of steam at a pressure of eighty 
pounds to the square inch, and when it goes into the atmosphere 
it will expand into over 6,000 cubic inches, at fifteen pounds 
pi'essure to the square inch, or the same pressure as the atmos- 
phere. This 1,000 cubic inches of steam which we dumped out 
of the cylinder, is precisely the same quality of steam as the 
steam which w^e have penned up in the boiler; and which we have 
to be making new all the time in order to keep the engine run- 
ning. Such is the operation of the steam engine which receives 
its steam the full length of the stroke ; and such an engine may 
be described briefly, as a very wasteful machine which throws 
away steam as good as it receives it, and which requires the gen- 
eration of a cylinder full of full pressure steam for each stroke. 
It should be readily understood that when the piston has com- 
pleted its stroke, and just before the exhaust valve is opened to 
allow the steam to escape, the cylinder contains 1,000 cubic 
inches of steam at eighty pounds pressure, which it is capable of 
expanding into many tliousand (uibic^ inches at constantly de- 
creasing pressure. The first step in the improvement of such an 



HANDBOOK ON ENGINEERING. 387 

engine would be to so arrange things as to get some benefit from 
this enormous power of expansion. The full stroke engine does 
not get one-half of the power before it throws the steam away. 
The engine which we would have referred to would yield a power 
of 8,000 pounds moved ten inches at each single stroke; 33,000 
pounds moved one foot in one minute is a horse-power ; 66,000 
pounds moved half a foot would be the same. An engine using 
steam full stroke is such an extravagant contrivance that we, now- 
adays, seldom find them in use. There are certain classes of 
engines built, litted with link motions for driving the valve, and 
they are arranged so as to carry their steam full stroke, but pro- 
vision is also made for <piickly hooking up the link and suppress- 
ing the full-stroke feature. 

SLIDE VALVE ENGINES. 

If wc have an engine arranged to receive its steam full stroke 
and to dump the steam out into the air in as good condition as it 
was received, and we wish to get some of the benefits of the 
expansive power of the steam, there is a simple way of doing it 
and without any great ciiange in the engine, and that is, to 
lengthen out the slide valve so that after the cylinder is half full 
of steam, the valve will shut and let no more steam enter. Dur- 
ing the balance of the stroke, the entire power comes from the 
gradual expansion of the steam shut up in the cylinder, and it 
will be readily seen that whatever power we succeed in getting out 
of the expansion of the steam, is pure gain. The lower the pres- 
sure of the steam is when it is exhausted into the air, the more it 
has expanded, the more power we have gotten out of it, and the 
more we have gained. It may be said in a few words, that all 
slide-valve engines are now arranged to work their steam expans- 
ively . But it is, unfortunately, found that the slide-valve pos- 
sesses a peculiar defect which prevents the system being carried 
ver}^ far. We can lengthen out a slide-valve so as to cut the 



338 HANDBOOK ON ENGINEERING. 

steam off at any desired point of the stroke, and we must then 
increase the throw of the eccentric in order to properly operate 
the long valve. But the minute we do this we find that we have 
interfered, to a certain extent, with the proper operation of the 
exhaust. No matter what we do about the admission of steam or 
about cutting off before the end of the stroke, we must arrange 
our exhaust to take place at a certain point at the end of the 
stroke. It is found in practical operations that this necessary 
quality of the slide-valve prevents our arranging it to cut off the 
steam properly at an earlier j^oint than about five-eighths or three- 
quarter stroke. The consequence is, that an engine with two-feet 
stroke will receive steam 18 inches, then have (5 in. of expansion. 
It may be fairly said, in a general way, that about all the slide- 
valve engines now manufactured, cut off the steam at about five- 
eighths or three-quarters stroke ; and it may ])e further said that this 
is about all we can get out of a slide-valve engine. Even the trifling 
expansion got from such engines as this, represents an immense 
amount of money in the course of a year in large establishments, 
but it is not good enough for anyone who seeks even a decent 
investment of money, in power-getting appliances. 

REGULAR EXPANSION ENGINES. 

A liberal expansion of steam being desirable and the slide- 
valve proving totally incapable of providing for such expansion, 
the first step in the desired direction is to totally discard the 
slide-valve. The Corliss valve is a cylindrical piece, oscillating 
in a cylindrical hole. The valve does not fill this hole, but seats 
against one side only. Hence, the fitting qualities are about the 
same as with the slide-valve and, in fact, the principle is about 
the same, the Corliss representing a portion of the slide-valve, 
rolled into the form of a cylinder and operating in a concave seat. 
We must not only discard the slide-valve arrangement, but in 
the valve arrangement which we select, we must secure an abso- 



HANDBOOK ON ENGINEERING. * 339 

lute independeuce between the steam admission part of the sys- 
tem and the exhaust part. The slide-valve is one chunk of cast 
iron, letting in and cutting off steam at its outside edges, and 
opening and closing the exhaust by its inside edges. When one 
of these valve edges moves, everything else has to move. There 
is, consequently, no independence of action. In the Corliss 
engine there are parts to let steam into the cylinder and to quit 
letting it in at the proper time, and there are valves to let it out 
at the proper time, and they are perfectly independent of each 
other in all of their movements. The consequence of this 
arrangement is, that the steam valve may open, steam (k)w into 
the cylinder, the valve suddenly shut and chop the steam off 
short, the piston move forward in its stroke by the expansion of 
the confined steam, and finally, be let out by the opening of the 
exhaust val.ve, which has all the time stood ready for the dis- 
charge. Here we have a regular expansion engine. We can cut 
the steam off as early in the stroke as we desire, and hence, have 
any degree of expansion we desire. And we can do this without 
interfering with the exhaust valves. It is found, in practice, 
that an euguie cutting off at about one-iifth of its stroke and 
expanding the other four-fifths, will yield the fairest practical 
economy. 

AUTOMATIC ENGINES. 

In order that those not posted may understand what is meant 
by the term "Automatic Engines," we will have to go back a 
step. Take, for instance, a full-stroke engine. It ought to be 
well understood how the ordinary governor does its work. Sup- 
pose, for instance, that there is no governor, and that we regulate 
the speed of the engine bj'^ having a man stand at the throttle-valve 
all the time. If the engine runs too fast, he shuts the throttle- 
valve a little. This makes the steam pipe so small that the steam 
cannot flow fast enough to keep the pressure up, and consequently, 



340 HANDBOOK ON ENGINEERING. 

the speed goes down. If the engine runs too slow, he opens the 
throttle-valve and lets the steam flow free, so as to maintain 
higher pressure. Thus it will be seen that the man at the throttle 
regulates the engine by altering the pressure with which the steam 
acts upon the engine. An ordinary engine governor is simply a 
man at the throttle. When the engine runs too fast the balls fly 
out, the governor valve shuts a little and the pressure of stean> 
entering the engine is reduced, and so on through all the 
changes continually taking place. All steam engines, in which 
the regulation of steam is effected by means of a governor operat- 
ing upon a throttle, are called throttling engines. They operate 
by reducing the pressure of the steam admitted to the engine, and 
thereby taking so much of the vitality out of the steam. Jt is 
entirely the wrong way to do it. After once spending our 
money to get up pressure in the boiler, we should make the 
greatest possible use of that pressure, so long as we are taking 
the steam from the boiler. It is, therefore, desirable that 
the full boiler pressure should be admitted to our cylinder ; 
and the question arises as to how we shall be able to regulate 
the speed if we do not tinker with this pressure. The Automatic 
Engine regulates the speed by the simple act of altering the point 
of cut-off. If the engine is cutting off at one-fifth stroke, we get 
a power equal to the incoming force of steam for one-fifth of the 
stroke, and the expansion of the steam for the other four-fifths of 
the stroke. If the engine runs too slow we cut the steam off a 
little later and thereby increase the average pressure during the 
expansion. The Automatic Engine, then, is an engine which cuts 
off the steam at an earlier point in the stroke, if the engine runs 
too fast, and cuts it off at a later point if it runs too slow. It is 
the duty of the governor to say just when the steam valve should 
close and not let any more steam into the cylinder. In the Cor- 
liss Engine the steam valves open wide at the beginning of the 
stroke and let full boiler pressure smack in against the piston. 



HANDBOOK ON ENGINKERING. 



341 



After the piston has advanced to, say one-lifth of its stroke, the 
valve shuts up as quick as a flash and the expansion begins. If 
the engine starts too slow, the governor will hold the steam valve 
open a trifle longer, but will not interfere with its full opening at 
the beginning of the stroke, or with its flash-like closing when 
the cut-off is to take place. During all these operations of the 
.governor and the admission valves, the exhaust valves are let 
entirely alone, and they continue their work unchanged. It will 
thus be seen that the expansion engine makes provision for the 
utmost economy in the use of steam, and with the automatic fea- 
ture added to it, provides that this economy shall not be sacrificed 
for the purpose of regulating the speed. 

THE GARDNER SPRING GOVERNORS. 

Constf ucti6n» — Two balls are rigidly connected to the upper 
ends of two flat, tapering, steel springs — the lower ends of the 
springs being secured to a revolving sleeve which receives rotation 
through mitre gears ; links connect the balls to an upper revolv- 
ing sleeve, which is free to move perpendicularly. 

The valve stem passes up through a hollow standard upon which 
the sleeves revolve, and is furnished with a suitable bearing in the 
upper sleeve ; the closing movement of the valve is upward, and 
is obtained in the following manner : The balls at the free ends of 
the springs furnish the centrifugal force and the springs are the 
main centripetal agency (gravity is not employed). As the balls 
fly outward, under the centrifugal influence, they move in a curved 
horizontal path which may be described as an arc, modified by a 
radius of changing length — the radius being represented by the 
length and position of the springs ; the links represent a radius 
of lesser length, while the sleeve to which the lower ends of the 
links are pivoted, being free to rise and fall, nullifies the effect of 
the links in determining the arc in which the balls travel. As the 



84-2 



HANDBOOK ON ENGINEERING. 



balls move outward in their peculiiir patii, the sleeve is drawn up- 
ward by the links, and, as the balls move inward, the sleeve is 
])ushed downward. Tlie change of speed is obtained by increas- 




THE GARDNER STANDARD GOVERNOR— CLASS ««A>' 

WITH AUTOMATIC SAFETY STOP AND SPEEDEI<. 



ing or decreasing the centripetal resistance, and accomplished by 
the action of a spiral spring pivoted against the lever, and by 
means of a shaft and arm against the valve-stem in the direction 
to open the valve ; a thumb-screw is used to adjust the compres- 



HANDBOOK ON ENGINEERING. '^43 

sion. A convenient Sawyer's lever is attaclied to the shaft, and 
a reliable automatic safety stop is furnished when desired. 

The cut on the preceding page represents the Gardner Standard 
Governor, Class "A." 

This is a Gravity Governor, having an Automatic Safety Stop 
and Speeder. It is made in sizes from 1^ inches to 16 in., 
and is especially adapted to the larger type of stationary engines. 
In action, the centrifugal force of the pendulous balls is opposed 
by the resistance of a weighted lever, the speed being varied by 
the position of the weight. The Automatic Safety Stop is very 
simple in construction and reliable in action. It is accomplished 
by allowing a slight oscillation of the shaft bearing, which is sup- 
ported between centers and held in position by the pull of the 
belt ; a projection at the lower part of the shaft bearing supports 
the fulcrum of the speed lever. If the belt breaks or slips off 
the pulley, the support of the fulcrum is forced back, so as to 
allow the fulcrum to drop and instantly close the valve. The 
valve is not affected by steam current and both valve and seats 
are made of special composition, that effectually resists wear 
and the cutting action of the steam. The workmanship is of the 
highest class, all parts being made by the duplicate system, with 
special machinery. 

The cut on the following page represents Class " B " Gov- 
ernor — a combination of the gravity and spring actions. 

They are made in sizes from J to 10 inches inclusive, and are 
adapted to all styles of engines. They are provided with Speeder 
and Sawyer's Lever, but are not automatic. In the Class " B " 
Governor the centrifugal force of the pendulous balls operates 
against the resistance of a coiled steel spring, inclosed within a 
case and pivoted on the speed lever by means of a screw ; the 
amount of compression of the spring can be changed so as to give 
a wide range of speed. A continuation of the Speed Lever makes 
a convenient Sawyer's hand lever, which controls the valve by 



344 



HANDBOOK ON ENGINEERING. 



means of a cord. Sizes | to 1^ in., inclusive, have an adjustable 
frame, which can be set at any desired angle in relation to the 




THE GARDNER STANDARD GOVERNOR — CLASSED." 



valve chamber. The valve and chamber are the same as used on 
Class " A " Governor, and they are made with the same care and 
style of workmanship. 



HANDBOOK ON ENGINEERING. 



B45 



CHAPTER XIV. 



A FEW REilARKS ON THE INDICATOR. 

The steam-engine indicator is an instrument designed to show 
the steam pressure in the cylinder at all points in the stroke. It 
consists primarily, of a piston of known area capable of moving 
in a cylinder and resisted by a coil spring of known strength. 
To this piston is attached, by means of suitable piston rod and 
levers, a pencil capable of tracing a line corresponding to the 
motion of the indicator piston. This line is traced on a paper 
slip attached to the drum of the indicator, which drum is con- 
nected to some moving part of the engine in such a way as to have 
a back and forward movement, coincident with the steam piston 
of the ensrine. 





By referring- to the above selected view of an Indicator, which 
is generally recognized as the best known, the construction will be 
readily understood . 



34(^ HANDBOOK ON ENGINEERING. 

THE USE OF THE STEAH ENGINE INDICATOR IN SETTING 
VALVES AND THE INVESTIGATION OF SOME OF THE DE= 
FECTS BROUGHT OUT BY THE INDICATOR CARDS. 

The steam-engfine indicator has come into such general use 
that to-day there are but few men running engines who are not 
familiar with its construction and manner of attachment to en- 
gines, and the method of calculating horse-power from cards. 
The indicator is attached to pipes tapped into the cylinder heads, 
or into the barrel of the cylinder opposite the counterbore, beyond 
the travel of the piston rings. The indicator consists of a cylin- 
der with piston and compression spring and a drum attached to a 
coiled spring, used for returning the same. The pressure of steam 
on the piston of the indicator compresses the spring above it. 
The motion of the piston is carried by a piston-rod to a pencil 
motion, which multiplies the motion of the spring some five or six 
times. The springs are marked 20, 40, 80, etc. This meaning 
that 80 lbs. pressure per square inch on the indicator piston 
(or whatever the spring may be marked) will cause the pencil 
at the end of the pencil-arm to move an inch. The pencil marks ■ 
on paper, which is fastened on a drum. This drum is moved by 
the crofes-head of the engine, through some form of reducing 
motion, such as pantograph, lazy-tongs, brumbo pulley, etc. To 
obtain the horse-power, we first need the mean pressure equiva- 
lent to the variable pressure on the card. This is most easily 
found by dividing the area of the card by the length, giving the 
height of a rectangular card of equivalent area, and then multi- 
plying this height by the scale of the spring. The mean effective 
pressure per square inch on the piston, times the area of the pis- 
ton in square inches, times the speed of the piston in feet per 
minute, divided by 33,000, gives the horse-power. If there is a 
loop at either end of the card, the area of this loop is to be sub- 
tracted from the larger area before finding the mean height of 



HANDBOOK ON ENGINEERING. -^47 

the card, since such a loop represents work opposed to the work- 
ing side of the piston. In getting areas by means of a planimeter, 
no attention need be given to the loops. By following the lines 
in order, as drawn by the indicator pencil, the loops will be sub- 
tracted from the main card, for if the main body of the card is 
traced in a right-handed rotation, the loops will be traced in a 
left-handed rotation. 

DIAGRAM ANALYSIS. 

Figs* t and 2 are from throttling engines ; the former repre- 
senting good performances for that class of engine, and the latter, 




Fig. 1. 

in some respects which the engineer will readily recognize, bad 
performances. 



348 HANDBOOK ON ENGINEERING. 

Figs* 3, 4, and 5, are from automatics; Fig. o representing 
what is now considered rather too light a load for best practical 
economy ; Fig. 4 about the best load, and Fig. 5 is from a con- 
densing engine. 

Line A B is the induction line, and B C the steam line ; both 
together representing the whole time of admission. 

G is about the point of cut-off, as nearly as can be determined 
by inspection. It is mostly anticipated by a partial fall of pres- 
sure due to the progressive closure of the valve. 

The usual method is, to locate it about where the line changes 
its direction of curvature. 

C D is the expansion curve. D is the j^oint of exhaust. 

D E is the exhaust line, which begins near the end of the stroke 
and terminates at the end of the stroke, or, at latest, before the 
piston has moved any considerable distance on its return stroke. 

The principal defect of Fig. 2 is, that this hue occupies nearly 
all the return stroke. E F is the back pressure line, which, in 
non-condensing engines, should be coincident with, or but little 
above, atmospheric pressure. In Fig. 5 it is below the atmos- 
pheric line to the extent of the vacuum obtained in the cylinder. 
Some authorities would call it the vacuum line in Fig. 5 but that 
name properly belongs to a line representing a j^erfect vacuum. 

F is the i3oint of exhaust closure (slightly anticipated by rise 
of pressure) and F A the compression curve, which, joining the 
admission line at A, completes the diagram proper, forming a 
closed figure. 

G^ 6r is the atmospheric line traced when the piston of the indi- 
cator is subject to atmospheric pressure, above and below alike. 
Some pull the cord by hand when tracing it, to make it longer 
than the diagram. H H is the vacuum line, which, when re- 
quired, is located by measurement such a distance below the 
atmospheric line as to represent the atmospheric pressure at the 
time and place, as nearly as can be ascertained. The mean 



HANDBOOK ON ENGINEERING. 



349 



atmospheric pressure at the sea level is 14.7 pounds. For higher 
altitudes, the corresponding mean pressure may be found by 
multiplying the altitude by .00053, and subtracting the product 
from 14.7. When a barometer can be consulted, its reading in 
inches multiplied by .49 will give the pressure in pounds. 




Fig. 2. 

1 is the clearance line, representing by its distance from the 
nearest point of the end of the diagram at the admission end, as 
compared with the whole length, the whole volume of clearance 
known to be present. Its use is mainly to assist in constructing 
a theoretical expansion curve by which to test the accuracy of the 
actual one. 

Calculating^ mean effective pressure. — Since the simplification 
and popularization of the planimeter, no engineer who has occa- 



350 



HANDBOOK ON ENGINEERING. 



sioii to compute the " indicated horse-power " (IHP) of engines 
should be without one ; for, if properly handled, the results 




Fio-. 



obtained by them are more accurate and more quickly obtained 
than by any other process. The diagram is pinned to a smooth 
board covered with a sheet of smooth paper, the pivot of the leg 
pressed into the board at a point which will allow the tracing point 
to be moved around the outline of the diagram without forming 
unnecessarily extreme angles between the two legs, and a slight 
indentation made in the line at some jwint convenient for begin- 
ning and ending ; for it is vitally important that the beginning and 
ending shall be at exactly the same point. The reading of the 
wheel is taken, or it is placed at zero, and the tracing point is 



HANDBOOK ON ENGINEERING. 



35.1 



passed carefully around the diagram, following the lines as closely 
as possible, moving right-handed, like the hands of a watch. The 
reading obtained (by finding the difference between the two, if 
the wheel has not been placed at zero) is the area of the diagram 
in square inches, which, multiplied by the scale of the diagram, 
and divided by its length in inches, gives the mean effective 
pressure. 

The process of finding the mean effective pressure by 
Ofdinatcs*. — Divide the diagram into 10 equal parts as shown by 
the full lines in Fig. 4 : but I wish to call attention to a frequent 
mistake, viz.. 




Fio 



making all the spaces equal. The end ones should be half the 
width of the others, since the ordinates stand for the centers of 



352 



HANDBOOK ON ENGINEERING. 



equal spaces. Ten is the most couvenient and usual number of 
ordinates, though more would give more accurate results. The 
aggregate length of all the ordinates (most conveniently measured 
consecutively on a strip of paper) divided by their number, and 
multiplied by the scale of diagram, will give the mean effective 




Fig. 5. 



pressure. A quick way of making a close approximation to the 
mean effective pressure of a diagram is, to draw line a 6, Fig. 6, 
touching at a, and so that space d will equal in area spaces c and 
e, taken together, as nearly as can be estimated by the eye. 
Then a measure,/, taken at the middle, will be the mean effective 
pressure. With a little practice, verifying the results with the 
planimeter, the ability can soon ))e accpiired to make estimates in 



HANDBOOK ON ENGINEERING. 



353 



this way with only a fraction of a pound of error with diagrams 
representing some degree of load. With very high initial pres- 
sure and early cut-off, it is not so available. 




/ 



Jt 



^ 



Fig. 6. 

The indicated horse-power* — IHP is found by multiplying 
together the area of the piston (minus half the area of the piston- 
rod section, when great accuracy is desired), the mean effective 
pressure and the travel of the piston in feet per minute, and 
dividing the product by 33,000. It is sometimes convenient to 
know the HP constant of an engine, which is the HP for one 
revolution at one pound mean effective pressure. This multiplied 
by the mean effective pressure, and by its number of revolutions 
per minute, gives the IHP. 



THEORETICAL CURVE. 

Testing expansion curves* — It is customary to assume that 
steam, in expanding, is governed by what is known as Mariotte's 
law, according to which its volume and pressure are inversely pro- 



354 



HANDBOOK ON ENGINEERING. 



portional to each other. Thus, if a cubic foot of steam at, say, 
100 pounds pressure be expanded to 2 cubic feet, its , pressure 
will fall to 50 pounds, and proportionately for all other degrees 
of expansion. The pressures named are " total pressures ; " that 
is, they are reckoned from a perfect vacuum. A theoretic ex- 
pansion curve which will conform to the above theory may be 




Fig. 7. 



traced by the following method : Referring to Fig. 7, having 
drawn the clearance and vacuum lines as before explained, draw 
any convenient number of vertical lines, 1, 2, 3, 4, 5, etc.,^ at 
equal distances apart, beginning with the clearance Hue and num- 
ber them as shown. Decide at what point in the expansion curve 



HANDBOOK ON ENGINEERING. 



355 



of the diagram you wish the theoretic curve to coincide with it. 
Suppose you choose line 10, on which you find the indicated pres- 
sure to be 25 pounds. Multiply this pressure by the number of 
the line (10) and divide the product (250) by the numbers of 
each of the other lines in succession. The quotients will be the 
pressures to be set off in the lines. Thus, 250 divided by 9 gives 
27.7, the pressure on line 9 ; and so for all the others. The 
same curve may also be traced by several geometric methods, one 
of which is as follows, referring to Fig. 8 : — 




Fi2:. 8. 



Having drawn the clearance and vacuum lines as before, 
select the desired point of coincidence, as a, from which draw the 
perpendicular a ^. Draw A B Sit any convenient height above or 
near the top of the diagram, and parallel to the vacuum line D C. 
From A draw A C and from a draw a h parallel to D C\ and from. 



356 HANDBOOK ON ENGINEERING. ; 

its intersection with A B, erect the perpendicular b c, locating the 
theoretical point of cut-off on A B. From any convenient num- 
ber of points in A B (which may be located without measurement) 
as J5J, F, G, H, draw lines to (7, and also drop perpendiculars E e, 
F f, G (/, Jlh, etc. From the intersection of E C with h c, draw a 
horizontal to e, and the same for each of the other lines F C, 
G 0, H C; establishing f)oints e,/, g, /i, in the desired curve. 
Any desired number of points may be found in the same way. 
But this curve does not correctly represent the expansion of 
steam. It would do so if the steam during expansion remained 
or was maintained at a uniform temperature ; hence, it is called 
the isothermal curve, or curve of same temperature. But, in fact, 
steam and all other elastic fluids fall in temperature during expan- 
sion, and rise during compression ; and this change of temperature 
augments the change of pressure slightly ; so that if, as before 
assumed, a cubic foot of steam at 100 pounds total pressure be 
expanded to two cubic feet, the temperature will fall from nearly 
328° to about 278°, and the pressure instead of falling to fifty 
pounds, will fall a trifle below 48 pounds. A curve in which the 
pressure due to the combined effects of volume and resulting 
temperature is represented, is called the adiabatic curve, or curve 
of no transmission ; since, if no heat is transmitted to or from the 
fluid during change of volume, its sensible temperature will 
change according to a fixed ratio, which will be the same for the 
same fluid in all cases. I need not attempt to give any of the 
usual methods of tracing the adiabatic curve, since the isothermal 
curve is the one generally used for that purpose. And while it is 
incorrect in that it does not show enough change or pressure for a 
given change of volume, the great majority of actual diagrams are 
still more incorrect in the same direction ; so that when a diagram 
conforms to it as closely as the one used in these illustrations, it 
is considered a remarkably good one. A suflSciently close 
api3roximation to the adial^atic curve to enable the non-profes- 



HANDBOOK ON ENGINEERING. 357 

sional engineer to form an idea of tlie difference between the two, 
may be produced by the following process : Taking a similar 
diagram to those used for the foregoing illustrations, we fix on a 
point A near the terminal, where the total pressure is 25 pounds. 
As before, this point is chosen in order that the two curves may 
coincide at that point. Any other point might have been chosen 
for the point of coincidence ; but a point in that vicinity is generally 
chosen so that the result will show the amount of power that 
should be obtained from the existing terminal. This point is 3.3 
inches, from the clearance line, and the volume of 25 pounds is 
9% ; that is, steam at that pressure has 996 times the bulk of 
water. Now, if we divide the distance of A from the clearance 
line by 996, and multiply the quotient by each of the volumes of 
the other pressures indicated by similar lines, the products will be 
the respective lengths of the lines measured from the clearance 
line, the desired curve passing through their other ends. Thus, 
the quotient of the first, or 25-pound pressure line divided by 
996 is .003313; this multiplied by 726, the volume of 25-pound 
pressure, gives 2.4, the length of the 25-pound pressure line ; and 
so on for all the rest. 

Fig* 9 shows a card taken from a Corliss engine, running at a 
speed of about ninety revolutions per minute. On account of the 
slow speed and the quick 
admission obtained by this 
form of valve gear, but lit- 
tle compression is needed. 
For high speed engines, 
there is much more com- 
pression. At high speeds, 

the expansion line of the — — 

indicator card, instead of ^^' 

being a smooth curve like that shown in Fig. 9, is often a wavy 

line, due to oscillations of the spring in the indicator. 





358 HANDBOOK ON ENGINEERING. 

Figf. to reiDreseiits what is called a stroke card. The indicator 

shows us the pressure on 
one side of the piston for 
a revolution. When we 
calculate the horse-power 
from a card, we are as- 
suming that the back pres- 
sure and compression 
line on the other side of 

-_^. , ^ the piston are the same as 

F12;. 10. 

shown on the card. This 

may or may not be the case.- In calculating the total horse-power 
for the two ends of the cylinder, an}^ error from this cause affect- 
ing the calculation for one end of the cylinder, will be nearly 
balanced by an opposite error in the calculations for the other end, 
so that the final result is practically correct. If it were not for 
the j)iston-rod making the area of one side of the piston smaller 
than on the other, there would be absolutely no error arising 
from this. The stroke card shows the pressure on opposite 
sides of the piston at all points of the stroke. The difference 
between the hues at any point is the effective push per square 
inch. This card is constructed by using the steam and expan- 
sion lines of the card from one end, and the back pressure 
and compression lines for the same stroke, from the card taken 
on the other end. In constructing diagram for very accurate 
work, the ratio of the areas of the two sides of the piston have 
to be considered ; the pressure above the atmosphere for one 
side being multiplied by this ratio. It will be seen that up to 
the point of cut-off, the difference of pressure, or effective pres- 
sure, is nearly constant; this difference grows less, due to the 
drop along the expansion curve, till at the j^oint where the 
two lines cross, the pressure on the two sides balances. Be- 
yond this point, the pressure exerted to hold the piston back 



HANDBOOK ON ENGPNEERING. 



359 



is greater than that exerted to push it ahead. The energy stored in 
the fly-wheel during the first part of the stroke is given out here 
near the end of the stroke to help the engine over the dead point. 

STEAH CHEST CARDS. 

By attaching- one indicator to the steam chest of an engine, 
and another to one end of the cylinder, it can be seen 
whether the pipes and ports are of sufficient size. A 
sloping steam line on an indicator card may be due to too 
small a steam pipe, or too 
small steam ports, or to 
both of these combined. 
This does not apply, of 
course, to engines using 
throttling governors. 

Fi^, i t shows the effect 
of too small steam pipe. 
When steam is admitted 
to the cylinder, there is a 
drop in pressure in the 




Fig. 11. Steam Chest on Forward 
Stroke. 

chest. This drop becomes greater in amount as the speed of the 

piston increases. At cut- 
off , the flow of steam into 
the cylinder stops, then 
the pressure in the chest 
reaches boiler pressure. 
If there is no great drop 
in the line on the steam 
chest card, and a consid- 
erable drop in the steam 
line of the card, it would 
mean that the ports are 




Fig. 12. Steam Chest Card on 
Forward Stroke. 



too small. Such a case is shown by Fig. 12. 



360 



HANDBOOK ON ENGINEERING. 




Fig. 



13. Steam Chest Card on 
Forward Stroke. 



If there i« a drop in 
the chest line up to cut- 
off, and a still greater 
drop in the steam line 
of the card, it would 
indicate that both the 
steam ports and the 
steam pipe were too 
small. Fig. 13 shows 
such a case. 




ECCENTRIC OUT OF PLACE. 

Figs^ i4, tS, \6f and 17, show cards taken from a Corliss En- 
gine having the eccentric out of adjustment. Similar cards would 
be obtained from any en- 
gine having all the valves 
moved by one eccentric. 
The plain slide valve and 
the locomotive, especially 
in full gear, would give 
similar cards for the same 
derangements of eccen- 
tric. 

Fig* J 4 was taken with 
the eccentric a trifle less 
than 90° ahead of the crank, or about 20° behind where it belongs 
on this particular engine. 

Fi^. i5 shows the eccentric moved too far ahead of the crank. 

By comparison with Fig. 9, it will be seen that moving the 
eccentric back makes all the events of the stroke, such as admis- 
sion, release and compression and cut-off, in the case of engines 
without automatic cut-off governor, come later ; while moving 
the eccentric ahead brings these events earlier. 




Figs. 14 and 15. 



HANDBOOK ON ENGINEERING. 



361 





Figs. 16 and 17. 



Figs* t6 Jiiid 17 are similar to Figs. 14 and 15, the only differ- 
ence being that eccentric is moved a greater distance out of place. 

In Fig* \6 the admission 
is very late. Release does 
not occur until after the 
piston has started on the 
return stroke, the steam, 
until released, being com- 
pressed back along the ex- 
pansion curve. This com- 
pression is always a trifle 
below the expansion line, 
due to the fact that some of the steam has condensed in the 
interval between the end of the stroke and the release. 

Fig* 17 shows too much compression and too early a release. 
Steam is compressed above boiler pressure in the cylinder, when 
the valve lifts and the steam escapes into the chest. 

Cards like Figs. 14 and 15 are very common. 

ECCENTRIC CARDS. 

As small distances near the ends of the indicator cards repre- 
sent a large angular motion of the crank, the events occurring at 
the ends of the card are so squeezed together that it is hard to 
tell from the card just what any peculiarity in the lines may be 
due to. The eccentric rod working the valves of the engine will 
be moving at its greatest speed when the crank is near the centers 
and the piston near the ends of the stroke ; since the eccentric is 
about 90° ahead of the crank. If the motion of the indicator 
drum is taken from the eccentric rod instead of the cross-head, the 
card will be changed in shape, compression and release coming 
near the middle of the card, and being spread out over consider- 
able length, the cut-off, expansion and back pressure lines coming 
near the ends of the card. 



362 



HANDBOOK ON ENGINEERING. 



Fig» J 5 gives a steam card drawn, assuming thai the expansion 
and compression lines are hyperbolic. The eccentric card for this 

had been plotted, and cor- 
responding points marked 
with the same letters. The 





Fig. 18. 



Fig. 19. 



compression curve, extending from jP to A, is a double curve. 
Admission occurs at A, cut-off at B, release at (7, and compres- 
sion at F. 

Figs. i9 and 20 show cards taken from an engine having tight 
valves and a tight piston. Corresponding points on the two cards 

are lettered the same. For a 
cut-off later than half stroke, 
the steam line on the eccen- 
tric card doubles on itself, as 
shown in Figs. 21 and 22. 

The peculiar bend shown 
by the dotted lines on com- 




Fig. 20. 

pression curve of the steam card, 
Fig. 18, is developed on the 
eccentric card into a well marked 
flat place. Evidently this rep- 
resents a loss of pressure at this 
point, which may be attributed 
to one or more of three causes : 
first, leakage by the piston; 



Fig. 21. 
second, leakage by the exhaust valves ; third, a rapid condensa- 




HANDBOOK ON ENGINEERING. 363 

tion of steam. If a leakage, it is probable that there is steam 
blowing by all through the stroke. 
Near the end of the stroke the pis- 
ton is moving at so slow a rate that 
the leakage overbalances the com- 
pression. It frequently happens 

that the pressure drops off at the 

end of compression, making the Fig. 22. 

upper end of the compression line 

resemble an inverted letter U. If the leakage is by the piston, 
it will appear or may be made to appear near release, as will be 
explained later. The effect of compressing steam is to dry it, 
or, if dry already, to superheat it. While it may be possible in 
some cases for some of the drop here to be due to condensation, 
in the majority of cases leakage is the trouble. 

Fig* 23 shows the effect of a bad leakage by the piston. This 
leakage is made evident by the appearance of the upper end of 

the compression curve 
and by the increase in 
pressure along the expan- 
sion line just before re- 
lease. By referring to 
the stroke card, it will be 
seen that near this point 
Pig, 23. ^^ pressures on the oppo- 

site side of the piston are 
the greater, so that the leakage is now into the side on which the 
card is being taken. Unless compression on one side comes 
earlier than release on the other side, this method would fail. 
In most engines the valves are set so that compression does 
come earlier, and all four valve engines can be easily set so 
as to delay release on one end, and to hasten compression on the 
other end. In the case of a Corliss engine, this means; simply 




»HB4 HANDBOOK ON ENGINEERING' 

the changing the length of the rods leading from the wrist plate 
to the valve arm. This change can be made with the engine run- 
ning. It is possible that a card hke Fig. 23 might be obtained 
from a four-valve engine having a leaky steam valve on one end 
and a leaky exhaust valve on the other end. 

Fig* 24 represents the head end and the crank end cards 
taken from a plain slide valve engine. The valve has equal 
steam laps and equal exhaust laps. The only trouble in this case 




Fig. 24. 

is that the valve spindle is too short. Shortening the valve spin- 
dle decreases the outside lap of the valve and increases the inside 
lap for the head end side, and increases the outside lap and de- 
creases the inside lap for the crank end side. As will be seen by 
the cards, the head end has the cut-off lengthened, the release 
delayed, and the compression hastened; the crank-end has the 
cut-off shortened, the release hastened, and the compression de- 
layed. If the valve spindle were too long the cards shown would 
be interchanged, the crank end card being the one marked head 
end. 

THE STEAM ENGINE INDICATOR. 

Benefits derived and information ascertained from its use* — 
The benefits derived, and the information ascertained from the 
use of the steam-engine indicator are varied and important. 



HANDBOOK ON ENGINEERING. 365 

" The office of the indicator is to furnish a diagram of the 
action of the steam in the cylinder of an engine during one or 
more revolutions of the crank, from which is deduced the follow- 
ing data : Initial pressure in cylinder ; piston stroke to cut-off ; 
reduction of pressure from commencement of piston stroke to cut- 
off ; piston stroke to release ; terminal pressure ; gain in econ- 
omy due expansion ; counter pressure, if engine is worked, 
non-condensing ; vacuum as realized in the cylinder, if engine is 
worked condensing ; piston stroke to exhaust closure, usually 
reckoned from zero point of stroke ; value of cushion ; effect of 
lead and mean effective pressure on the piston during complete 
stroke. The indicator diagram, when taken in connection with 
the mean area and stroke of piston and revolution of crank 
for a given length of time, enables us to ascertain the power de- 
veloped by engine ; and when taken in connection with the mean 
area of piston, piston speed and ratio of cylinder clearance, 
enables us to ascertain the steam accounted for by the engine. 

" The mean power developed by engine compared with the 
steam delivered by boilers, furnishes cost of power in steam, 
and when compared with the coal, furnishes cost of the power in 
fuel. 

" The diagram also enables us to determine with precision the 
size of steam and exhaust ports necessary, under given conditions, 
to equalize the valve functions ; to measure the loss of pressure 
between boiler and engine ; to measure the loss of vacuum be- 
tween condenser and cylinder ; to determine leaks into and out 
of the cylinder ; to determine relative effects of jacketed and 
un jacketed cylinders ; and to determine effects of expansion in 
one cylinder, and in two or more cylinders." 

TO TAKE A DIAGRAM. 

Connecting-cord* — The indicator should be connected to the 
engine cross-head by as short a length of cord as possible. Cord 



36(3 HANDBOOK ON ENGINEERING. 

having very little stretch, such as accompanies the instrument, 
should be used ; and in cases of very long lengths, wire should 
be used. The short piece of cord connected with the indicator is 
furnished with a hook; and at the end of the cord, connected 
with the engine, a running loop can be made by means of the 
small plate sent with each instrument ; by which the cord can be 
adjusted to the proper length, and lengthened or shortened as 
required. 

Selecting a spring, — It is not advisable to use too light a 
spring for the pressure. Two inches are sufficient for the height 
of diagram, and the instrument will be less liable to damage if 
the proper spring is used. The gauge pressure divided by 2 
will give the scale of spring to give a diagram two inches high at 
that pressure. 

To attach a card* — This may be done in a variety of ways, 
either by passing the ends of it under the spring clips, or by 
folding one end under the left clip, and bringing the other end 
around under the right ; but, whatever method is applied, care 
should be taken to have the card rest smoothly and evenly on the 
paper drum. Now attach the cord from the reducing motion to 
the engine ; but be certain the cord is of the proper length, so as 
to prevent paper drum from striking the inner stop in drum 
movement on either end of the stroke. 

Tension of drum spring* — The tension of the drum spring 
should be adjusted according to the speed of the engine ; in- 
creasing for quick running, and loosening for slower speeds. 

The steam should not be allowed into the indicator until it has 
first been allowed to escape through the relief on side of cock, to 
see if is clean and dry. If clean and dry, allow it into the indi- 
cator, and allow piston to play up and down freely. 

Before taking diagram, turn the handle of cock to a horizontal 
position, so as to shut off steam from piston, and apply pencil to 
the paper to take the atmospheric line. 



HANDBOOK ON ENGINEERING. 



367 



In applying pencil to the card, always use the horn-handle 
screw, to regulate pressure of pencil upon paper to produce as 
fine a line as possible. After the atmospheric line is taken, turn 
on steam, and press the pencil against card during one revolution. 

When the load is varying, and the average horse-power re- 
quired, it is better to allow the pencil to remain during a number 
of revolutions, and to take the mean effective pressure from the 
card. 



Fig. 25. 
Fig. 25 was taken from a Russell engine 13"x20", running 
205 revolutions per minute, boiler pressure 98 lbs., scale of indi- 
cator 60 lbs. Duty, electric lighting. 



After sufficient number of diagrams have been taken, remove 
the piston, spring, etc., from the indicator, while it is still upon 
the cylinder ; allow the steam to blow for a moment through the 
indicator cylinder; and then turn attention to the piston, spring, 
and all movable parts, which may be thoroughly wiped, oiled and 
cleaned. Particular attention should be paid to the springs, as 
their accuracy will be impaired if they are allowed to rust ; and 
great care, should be exercised that no grit or substance be intro- 
duced to cut the cylinder, or scratch the piston. Be careful 



368 



HANDBOOK ON ENGINEERING. 



always not to bend the steel bars or rods. The heat of the steam 
blown through the C3^1inder of the indicator will be found to have 
dried it perfectly, and the instrument may be put together with 
the assurance that it is all ready for use when required. Other 
items of precaution should be borne in mind. Any engineer 
can easily repeat this operation without further instruction. 



Fig. 26. 

Fig. 26 was taken from a Russell engine 16"x24", running 
157 revolutions per minute, boiler pressure 70 lbs., scale of indi- 
cator 40 lbs. Duty, flouring mill. 





Friction indication. Full Load Indication. 

Harjrisburg Ideal Simple Single Valve Engine. 



Fig. 27. 



Fig. 28. 



HANDBOOK ON ENGINEERING. 



369 





Extreme Load Variation 
Indication. 



Graduated Load 
Indication. 

Harrisburg Ideal Simple Single Valve Engine.) 
Fig. 29. Fig. 30. 





High Pressure Indication. Low pressure Indication. 

Harrisburg Ideal Compound Single Valve Engine, 



Fig. 31. 



Fig. 32. 





friction Indication. Full Load Indication. 

Harrisburg standard Simple Single Valve Engine. 



Fig. 33. 



Fig. 34. 



370 



HANDBOOK ON ENGINEERING. 





Friction Indication. Full Load Indication. 

Harrjsburg Standard Simi'LE Four-Valve Engine. 
Fig. 35. Fig. 36. 





High Pressure Indication. Low. Pressure Indication-. 

Harrisburg Standard Compound Four-Valve Engine. 



Fig. 37. 



Fig. 38. 



Figs* 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37 and 38 are 
cards taken from the Harrisburg Ideal and Standard Engines. 
An engineer will see from these cards the kind of card he should 
get from a high speed engine of this class. 



Fig* 39 is from a Frick Corliss Engine., driving a Frick Com- 
pressor: — 

Steam Cylinder 19"x28". 

Steam - . 95 lbs. 

Revs 58 

Cond, Press 164 lbs. 

Back Press 27 lbs. 



HAl^DBOOK ON ENGINEERING. 



371 



Engine, 19" x 28", 
Steam, 95 lbs. 
Revs. 58 lbs. 
Cond. Press., 164 Ms. 
Back Press. , 27 Ms; - 



Fig. 39. 



INDICATOR DIAGRAMS FROM SO-TON "ECLIPSE" 
MACHINE. 



R. Hand Pump^ 
12^" s 28". 
.Sca^e. 120 Ihs. 




Fig. 40. 
Fi^. 40 is R. Hand Pump. 121" x 28". Scale, 120 lbs. 



372 



HANDBOOK ON ENGINEERING. 



L.-Hand Pitmp. 
12i" X 28". 
Scale, 120 M*. 



Fig. 41. 
Fig* 41 is L. Hand Pump. 271" x 28". Scale, 120 lbs. 



Engine, 80" x 36" 
Steam, 75 Ihs. 
Revs. 44 

Cond, Press., 162 /6«, 
Back Press., 10 lbs. 



Fio;. 42. 



Fig's* 42, 43 and 44 are diagrams from a 100-ton " P>lipse 
Machine." 



HANDBOOK ON ENGINEERING. 



373 



INDICATOR DIAGRAMS FROM lOO-TON "ECUPSg" 
MACHINE, 



R, Hand Pumpi 
17" X 36". 
Scale, 80 Ib^ 




Fiff. 43. 



L. Hand Pump^l 
17" X 36". 
Scaler 80 Ids 




Fig. 44. 



374 



HANDBOOK ON ENGINEERING. 




HANDBOOK ON ENGINEERING. 



375 



It will be interesting to note that when the eccentric is simply 
moved forward or backward around the shaft by the action of the 
governor, all the events of the stroke — admission, release, cut-off 
and compression — will be hastened or retarded together ; but if 
the eccentric be so designed that the governor will shift it across 
the shaft instead of around it, the admission and release will be 
effected differently, and in the opposite direction from the cut-off 
and compression. If, for example, the cut-off is made to occur 
earlier in the stroke, the compression will occur earlier also, but 
the admission and release will occur later instead of earlier. By 
combining the two movements of the eccentric and having the 
governor move it partly around and partly across the shaft, it is 
possible to keep the admission and release nearly constant, while 
the cut-off and compression vary. This result is attained to a 
certain extent in the best single-valve engines. Besides these two 
types, there are numerous other styles of engines in which the 
point of cut-off is varied automatically. Instead of a shaft gov- 
ernor with a shifting eccentric, a weighted pendulum governor is 
sometimes employed to operate the link, or radius rod of some 
one of the various link motions. Sometimes there are separate 
admission and exhaust valves, the former being under the con- 
trol of a shaft governor, and the latter operated hy a fixed eccen- 
tric, so that the points of admission and cut-off only are varied, 
while the points of release and compression, which depend upon 
the exhaust valve, remain fixed. There are a great many modifi- 
cations of the Corliss engine, as originally constructed by 
Geo. H. Corliss, and there are many engines which, while not re- 
sembling the Corliss engine, have some arrangement whereby the 
cut-off valves are tripped. 

On pag'es 374 and 376 is a collection of diagrams which 
illustrate verj^ nicely the peculiarities and difference in the action 
of tlirottling and automatic engines. The four diagrams on 
page 374 were taken from a Ball automatic, in an electric light 



376 



HANDBOOK ON ENGINEERING. 




HANDBOOK ON ENGINEERING. 377 

station. The first diagram was taken late in the afternoon when 
the engine was started and before any load was thrown on to the 
machine, and the three succeeding cards were taken at intervals 
later in the evening as the number of lights increased and the 
load became heavier. Two or three important points are to be 
noticed in connection with these diagrams. First, the initial 
pressure of the steam at the point of admission is very nearly the 
same in all four cards, the slight variations being due chiefly to a 
variation in the boiler pressure. Second, the length of the cut-off 
increases with the load. The compression also becomes later as 
the cut-off lengthens, and while there is also a change in the points 
of admission and release, it is not as marked as the changes in cut- 
off and compression, for reasons that have already been explained. 

Takings the cards on page 376, we have four excellent examples 
of the action of a throttling engine. These cards are from a 
Dickson engine, taken at the same station and under the same 
conditions as the Ball engine cards, with the exception that in 
this case both head and crank-end diagrams were taken on the 
^ame cards, while only the head end diagrams from the Ball 
engine are shown. The two sets of diagrams are well adapted 
for comparison, because both engines are of the single-valve type, 
with the valve moved by one eccentric. 

The points to be noted are, first, that the points of cut-off are 
the same, namely at about | stroke, in all the throttling cards, 
and second, that the power of the engine is increased by the action 
of the governor in opening a throttle valve wider, allowing steam 
to enter the cylinder at higher pressure. 

It was stated at the outset that automatic regulation is the 
most approved method for regulating the speed of steam engines 
at the present time. It is generally believed and it is probably 
true, that automatic engines give better economy than throttling 
engines and that they regulate a little more closely. It will 
readily be seen that when the governor of the automatic engine 



378 HANDBOOK ON ENGINEERING. 

changes position, it measures out just the quantity of steam that 
will be required to keep the engine within the speed limits during 
the following stroke. The effect of this regulation, moreover, is 
felt at one point in the stroke only — the point of cut-off — so that 
any change in the governor up to the time when the piston nears 
the point of cut-off will produce an immediate change in the 
quantity of steam admitted. In the throttling engine, on the 
other hand, the regulation is effected during the whole stroke up to 
the point of cut-off, and the full effect of any change of the gov- 
ernor cannot be felt until the next stroke. With regard to the 
relative economy of the two types, it should be kept in mind that 
the throttling engine is generally of cheap construction, has large 
clearance, a single, unbalanced slide-valve that does duty for both 
entering and exhaust steam and aside from the throttling feature, 
is inferior to the average automatic engine. It is reasonable to 
suppose, therefore, that at least a part of the large steam con- 
sumption generally attributed to the throttling engine is due to 
its inferior design and construction and not to its method of 
governing. 

For example, take the case of the Ball and the Dickson engines, 
from which I have shown cards. They both have a single slide- 
valve, but the former runs at higher speed than the latter and its 
valve is balanced, so that for these reasons it would be expected 
to be a little more economical. "We should not expect, however, 
that a test would show any decided superiority that could be 
attributed to the method of governing. If we were to compare 
the average throttling engine with the most approved type of 
automatic engine, like the Corliss, we should find that the effi- 
ciency of the latter was much higher. The gain, however, would 
be due to a large extent to the small clearance spaces, separate 
steam and exhaust valves, and other important features of the 
Corliss engine, rather than to its automatic cut-off. It is not 
the purpose to discuss here why these features give improved 



HANDBOOK ON ENGINEERING. ^79 

economy over the single valve, but simply call attention to the 
fact that they exert an important influence. The exact influence 
which the throttling or automatic features exert apart from the 
general constructive features of the engine is hard to determine. 
It is known that high-pressure steam is more economical to use 
than low pressure steam and the automatic engine, which pre- 
serves nearly the boiler pressure up to the point of cut-off, gains 
on this account. On the other hand, it is known that the most 
economical point of cut-off for a non-condensing engine is about 
one-third stroke, and when it becomes very much less than this 
there is a serious drop in the economy. A. very short cut-off 
with high-pressure steam produces so great a variation in the 
temperature during one stroke of the piston that the cylinder 
condensation becomes excessive. For very light loads, therefore, 
it would be better to throttle the steam than to shorten the cut-off. 
It is necessary for all engines to have a reserve of power and 
hence the cut-off of throttling engines must come late in the 
stroke. If it were early in the stroke, there would not be enough 
reserve power with the reduction in the pressure of the steam that 
is necessary with this type. The late cut-off produces poor 
economy when the load is heavy, because there will then be a 
high terminal pressure, and a large amount of heat, corresponding 
to this pressure, will be thrown away. A throttling engine there- 
fore, may be expected to do better at light loads than at heavy 
ones, and in fact, may do a little better at light loads than the 
automatic engine. If a throttling engine could be run so as not 
to vary much from its most economical load, and could be de- 
signed to have the good features of the best automatic engines, 
with the cut-off at an earlier period in the stroke, it would prob- 
ably be nearly or quite as well as the automatic engine. Under 
the conditions that they have to run, however, the automatic engine 
will keep the lead, although, as explained above, its superiority 
is not due entirely to the automatic feature. 



380 HANDBOOK OF ENGINKEKING. 



CHAPTER XV. 

Engineers over the country have been discussing whether or 
not more steam is used when an engine is made to run faster without 
changing either the cut-off or the back pressure. Some, strange as 
it may seem, have actual^ held to the opinion that, since the cut- 
off is not changed, no more steam is used, and hence, if it were 
possible to make an engine run faster without changing the cut-off , 
it would be doing more work than before without any increase in 
the consumption of steam. Of course, this is wrong. The speed 
of an engine, almost any engine, may easily be increased without 
changing the cut-off, and when this is done, the engine will do 
more work and will use more steam. It is utterly impossible to 
get something for nothing out of a steam-engine, or out of any 
engine or appliance. The only way in which a steam-engine can 
be made to do more work without using more steam is to increase 
its efficiency. And when everything else i^ kept the same and the 
speed only of an engine increased, the efficiency is very slightly 
increased. The condensation is decreased with an increase of 
speed, but the decrease would be so slight for most cases that it 
would hardly be worth considering. When an engine is cutting 
off at a certain part of the stroke, it uses at every stroke a cer- 
tain weight of steam which depends upon the initial pressure of 
the steam, clearance volume of the engine and the point of cut- 
off. If the engine makes 400 strokes per minute (200 revolu- 
tions, if a double acting engine) the weight of steam used will be 



HANDBOOK ON ENGINEEKING. 381 

400 times the weight used in one stroke ; but if the engine be 
made to make 500 strokes per minute, the weight of steam used 
per minute will be, neglecting the small difference in condensa- 
tion, 500 times the weight used in one stroke. 

HOW TO INCREASE THE SPEED, OR INCREASE THE POWER 
OF A CORLISS ENGINE. 

There are three ways in which this can be done. Take, for 
example, a 24"x48" simple Corliss engine making 70 revolu- 
tions per minute, the boiler gauge pressure 80 lbs. per square 
inch, one-quarter cut-off, or cut-off 12 inches from the beginning 
of the stroke; the mean effective pressure, say about 42 lbs. per 
sq. in., the governor pulley on the main shaft 10 inches in diam- 
eter, the pulley on the governor shaft 7 in. in diameter, and the 
friction of engine, cylinder clearance, condensation, etc., left 
entirely out of the question. It is desired to increase the speed 
of this engine to 80 revolutions per minute, and in this manner 
increase its horse-power. 

First methods — Regardless of piston rod, the area of the pis- 
ton is 452.4 square inches, nearly. The piston speed of this 
engine is 560 feet per minute, and its horse-power 322, nearly. 

452.4x42x560 
Thus: oo^iQp. =322. So that the horse-power of this 

engine at 70 revolutions per minute is 322, nearly, and this is 
what the manufacturer's catalogue gives. Now, in order to get 
80 revolutions per minute, take the 7-inch pulley off the governor 
shaft, and put in its place an 8-inch pulley. Thus: 70:80:: 
7:8. Then, the governor balls will revolve in the same relative 
plane that they did before, and the cut-off will remain the same; 
that is, at one-quarter, or 12 in. of the stroke. Thus, 7: 10:: 
70 : 100. And 8 : 10 : : 80 : 100. So the governor balls make 100 
revolutions per minute, both before and after making the change. 



382 HANDBOOK ON ENGINEERING. 

Now, with the engine speeded up to 80 revolutions per minute, 

we get 46 more horse-power. Thus: Piston speed equals 640 

452.4x42x640 
feet per minute. Then, oq^qq == 368 horse-power, 

nearly. And 368 minus 322 =46. Now, it would appear that 

we are getting 46 horse-power more for nothing, but such is not 

452.4x12x2x70 
the case. For, T798 =439.8-|-, or nearly 440 

cubic ft. of steam per minute, at 80 lbs. boiler pressure, are 

452.4x12x2x80 
required to develop 322 horse-power. And, v^ 

= 502.6-f- or nearly 503 cubic ft. of steam per minute, at 80 

lbs. boiler pressure, are required to develop 368 horse-power. 

Then, 503 minus 440 = 63 cubic feet more of steam at 80 lbs. 

boiler pressure, which means more water evaporated per minute 

and more coal burned per hour. 

Second method* — Retain the same engine speed and the same 

cut-off, but increase the boiler pressure from 80 to 90 lbs. Then 

80: 90: : 42 : 474-5 call it 48 lbs. mean effective pressure. 

452.4x48x560 
Then, qoqaq = 368 horse- power, nearly, the same as 

before, and as given in the manufacturer's catalogue. We are 

now using 440 cubic feet of steam per minute at 90 lbs. pressure, 

with an increase of 6 lbs. M. E. P. ; consequently, more coal per 

hour must be burned. 

Third method* — Retain the same boiler pressure, that is 80 

lbs., and weight the governor so as to make the balls revolve in a 

lower jDlane in order to give a later cut-off. Thus, 322 : 368 : : 

i:|. That is, the cut-off must take place at about | of the 

stroke instead of at J. Then, J:!:: 42:48. That is the 

M. E. P. will be 48 lbs. per square inch with a cut-off at | of the 

452.4x48x560 
stroke. Then, '^^OOO ~ = 368 horse-power, the same as 



HANDBOOK ON ENGINEERING. 383 

before. But, ^ of 48 = 13^, or 13.71 inches nearly, so that, 

instead of cutting off at 12 inches with 80 lbs. boiler pressure, 

we are cutting off at 13.71 inches and using 63 cubic feet more 

. ^ ^, 452.4x13.71x2x70 .^^ , 

steam per mmute. ihus, =: 50o, nearly. 

^ 1728 ^ 

And, 503 minus 440 =63, that is, we must use 63 cubic feet 

more of steam per minute at 80 lbs. boiler pressure, in order to 

get 46 more horse-power, which means the evaporation of more 

water per minute, and the burning of more coal per hour. 



HOW TO INCREASE THE HORSE=POWER OF AN ENGINE 
HAVING A THROTTLING GOVERNOR. 

There are three ways in which this can be done, also. We 
will take, for example, a plain slide-valve engine 10 x 16 inches, 
making 150 revolutions per minute, with -f^ cut-off, and M. E. P. 
say 31i lbs. per square inch, with a boiler pressure of 60 lbs. 
by gauge. The governor pulley on the main shaft 6 inches 
in diameter, and the pulley on the governor shaft 4 inches 
in diameter. The horse-power of this engine is about 30. 

Thus, ii^ =. 2| ft., and 150 x 2-| = 400 ft., the piston speed. 

^, 10 X 10 X. 7854x31. 5x400 on i, i 

Then, = 30 horse-power, nearly. 

33000 ^ -^ 

It is now desired to run the engine at 180 revolutions per 
minute in order to develop 6 horse-power more. In order to 
obtain these results, the governor pulley must be enlarged, so as 
to make the governor balls revolve in the same plane at 180 revo- 
lutions per minute, that they now do at 150 revolutions. Thus, 
4: 6:: 150: 225, that is, the governor balls are now making 
225 revolutions per minute. And 150: 180 ::4:4.8. Con- 
sequently, the governor pulley must be increased to 4.8 inches in 



384 HANDBOOK ON ENGINEERING. 

diameter. Then, 4.8: 6:: 180 : 225, that is, the governor balls, 
after the change, making the same number of revolutions as 
before. At 180 revolutions per minute, the piston speed is 480 

feet per minute. Thus, ^^^^ =2|. And, 180x2f = 480. 

^, 78.54x31.5x480 ^^ . i t^ • i,, 

inen, = 36 horse-power, nearly. It miffht 

33000 f y J » 

seem from the above that we are getting 6 horse-power more for 

nothing ; but such is not the case. For, cutting off at -f^ is 

equivalent to cutting off at 9 inches of the stroke. 

rp, 78.54x9x2x150 ^«o u- i;^ i 

Then, = 123 cubic ft. , nearly. 

1728 ' \ 

. , 78.54x9x2x180 ..r. u- * 4. i a ^ 

And, =147 cubic feet, nearly. And, 

1728 -^-.^ 

147 minus 123 = 24. So that for 6 horse-power more, we are 

using 24 cubic feet more of steam per minute, at 31.5 lbs. M. E. P. , 

which means more water evaporated per minute and more coal 

burned per hour. 

If the boiler pressure may be safely increased, we can get 6 

horse-power more out of the engine without increasing its speed, 

by running the boiler pressure up to 75 lbs. by gauge. Thus 75 

lbs. boiler pressure would give about 37.8 lbs. M. E. P. with -^q 

4. ** rr., 78.54x37.8x400 o^ , i 

cut-on. Then, =36 horse-power, nearly. 

33000 f ^ J . 

In this case no change should be made in the governor, nor in 
the speed of the engine. We can also get 6 horse-power more 
out of this engine by cutting off later, say at|, in order to get 
37.8 lbs. M. E. P. But a later cut-off is not desirable, because 
it is not economical of steam, and besides, it would require a new 
valve, new eccentric, or a change in the length of a rocker arm, if 
not a change of the valve-seat, because the travel of the valve 
would have to be increased. 



HANDBOOK ON ENGINEERING. 385 

HOW TO INCREASE THE HORSE=POWER OF AN ENGINE 
HAVING A SHAFT GOVERNOR. 

Suppose it is desired to increase the speed of the engine from 250 
to 275 revolutions per minute, cutting off at J stroke. In this 
case the governor springs should be so adjusted that the throw of 
the eccentric will be the same at 275 revolutions that it was at 250 
revolutions. This will require an increased consumption of steam 
per minute at the same initial cylinder pressure as before making 
the change, consequently more fuel will be required. If the speed 
of the engine is not to be changed, an increase of the horse-power 
may be obtained by increasing the initial cylinder pressure, if the 
condition of the boiler will so permits Or, the initial cylinder 
pressure may remain unchanged and the governor springs and 
levers SQ adjusted as to give a later cut-off, say at | or Jg- of the 
stroke, or whatever may be required to offset the increased per- 
manent load, the speed of the engine remaining unchanged. Any 
one of the changes above described would necessitate an increased 
consumption of fuel. 

HOW TO LINE THE ENGINE WITH A SHAFT PLACED AT A 
HIGHER OR A LOWER LEVEL. 

We will suppose the latter shaft not yet in place, but to be 
represented by a line tightly drawn. From two points as far 
apart as practicable, drop plumb lines nearly, but not quite, 
touching this line. Then by these strain another line parallel 
with the first, and at the same level as the center line of 
the engine, and at right angles with this stretch another represent- 
ing this center line, and extend both each way to permanent walls 
on which their terminations, when finally located, should be care- 
fully marked, so they can at any time be reset. The problem is 
to get the latter line exactly at right angles with the former. 
Everything depends upon the accuracy with which this right 



386 



HANDBOOK ON ENGINEERING. 



angle is determined. It is done by the method of right-angled 
triangles. There are two ways of applying this method. In the 
first, one end of a measuring line is attached to some point of 
line No. 1, and its other end is taken successively to points on 
line No. 2 on opposite sides of the intersection, as illustrated in 
the following figure, in which A B is 3i portion of line No. 1, and 
C D of line No. 2, the direction of which is to be determined. 
B F and B G are the same measuring line fixed at B, and applied 
to the line C D successively at the points F and G. The dis- 



tances B i^ and B G being, therefore, the same, when E F \s 
equal to E G, the lines A B and C D are at right angles with each 
other. In the second, application is made of the law that the square 
of the hypothenuse of a right-angle triangle is equal to the sum 
of the squares of the other two sides. Thus 32-^42=5^. So if 
the above figure E B = i, E F =z?}, and B F=b^ the angle at 
J5J is a right-angle. Any unit of measure may be used, a foot is 
generally the convenient one ; so any multiple of these numbers 
may be taken; as, for example, 6, 8 and 10. Respecting the 
comparative advantages of these two ways, the situation will often 
determine which is to be preferred. In the former, the diagoiuil 



HANDBOOK ON ENGINEERING. 387 

being the same line, fixed at B and brought successively to the 
points F and (?, its length is immaterial, though generally the 
longer the better ; and the only point to be determined is the 
equality of E F and E (r, which may be compared with each 
other by marks on a rod. In the latter, the proportionate 
lengths, 3, 4 and 5, or their multiples, must be exactly measured. 
It is better adapted to places where a floor is laid and the meas- 
urements can be transferred by trammels. The result should be 
verified by repeating the operation on the opposite side of the 
intersection at J5J, and when so verified we have, in fact, the first 
process, without the additional and unnecessary trouble of deter- 
mining the relative lengths of the lines. Care should be taken 
when a measuring line is used, to avoid errors from its elasticity. 
On this account, a rod is often employed. Points on the lines 
are best marked by tying on a white thread. 

HOW TO LINE THE ENGINE WITH A SHAFT TO WHICH IT IS 
TO BE COUPLED DIRECT. 

In this case, it is supposed that the engine bed and the bear- 
ings for the shaft are already approximately in position. They 
are leveled by a parallel straight edge and a spirit level. To line 
them horizontally, a line must be run through the whole series of 
bearings and continued to a permanent wall at each end, and its 
terminating points, when determined, carefully marked, as already 
directed. A piece of wood is tightly set in each end of each 
bearing and the surfaces of these are painted white or chalked. 
Then the middle of each piece being found by the compasses, two 
fine lines are drawn across it, equally distant from the middle, and 
having between them a space a little wider than the thickness of 
the line. This being then strained, nearly touching those blocks, 
or, if long, having its sag supported by them, the two marks on 
each block must be seen, one on each side of the line, with the 
line of white between. 



388 HANDBOOK ON ENGINEERING. 

HOW TO SET A SLIDE VALVE IN A HURRY. 

Open your cylinder cocks ; then open the throttle slightly, so 
as to admit a small amount of steam to the steam-chest. Roll 
your eccentric forward in the direction the engine runs, until 
steam escapes from the cylinder cock at the end where the valve 
should begin to open. Now screw your eccentric fast to the 
shaft. Roll your crank tojthe next center and ascertain if steam 
escapes at the same point, at the opposite end of the cylinder. 
If so, ring your bell and go ahead. You are all right and can run 
until an opportunity occurs to you to open your steam-chest and 
examine your valve. 

DO YOU DO THESE THINGS? 

A writer in a contemporary asks and answers the following 
pertinent questions : — 

Do you take a squirt-can in one hand and project a stream of 
oil as far as you can throw it, in order to save going to the oil 
hole itself ? 

If you do, don't do it any more ; willful waste is downright 
robbery. 

Do you use an oil can at all for oiling, except on emergency, or 
for the moment ? 

If you do, don't do it any more, for much better lubrications 
can be had by automatic apparatus. 

Do you keep an old tin coffee pot full of suet on the steam- 
chest, and every time you have nothing else to do, pour a dipper- 
f ul into the steam-chest ? 

If you do, stop it and get a sight-feed cup, which will save 
you the labor of slushing the cylinder and save the cylinder and 
valve-seats, the piston and follower, and all other places touched 
by the grease. 



HANDBOOK ON ENGINEERING. 3^^ 

Do you feed the boiler imtil the water is out of sight in the 
glass, then shut off the feed, put in a big fire and sit down in 
a dark corner with a four-horse brier pipe and smoke, until you 
happen to think that maybe the water is low ? 

If you do these things you should notify the coroner that some 
day his services will be needed, but it is better to cease the prac- 
tice mentioned before the coroner comes. 

Do you stop leaks about the boiler as fast as they occur, or do 
you wait until the places sound like a snake's den before you stir? 

If you do, you waste heat, which is the same word as money, 
only differently spelled. Every jet of hot water leaking from a 
steam boiler is just so much money thrown away, and if it was 
your money you would be bankrupt in a short time, in some 
boiler rooms. 

Do you take a screw wrench and yank away at a bolt or nut 
under steam pressure? 

If you do, there will come a time, sooner or later, when you 
will do so once too often, and either kill yourself or some one else. 
Bolts and nuts are liable to strip or break if tampered with under 
pressure, and they never tell any one beforehand when they are 
going to do it. 

Do you attempt to stoj) pounding in the engine by laying for 
the crank-pin as it comes round , and trying to hit the key once in 
a while ? 

If you do, ask the strap and neck of the connecting-rod how 
he likes it, when you don't hit the key and do hit the oil cup? 

Do you pack the piston by taking it out of the cylinder, lay- 
ing it on the floor, setting out the rings, and then when the piston 
will not go into the cylinder, try to batter it in with a four-foot 
stick of cord wood? 

If you do, you should reform, and pack the piston in the 
cylinder where it belongs, being sure to get it central by meas- 
uring from the lathe center in the end of the piston rod. 



390 



HANDBOOK ON ENGINEERING. 



Do you put a new turn of packing on top of the old, hard- 
burned stuff when the piston rod leaks steam ? 

If you do, you will have a scored piston rod and broken gland 
bolts some day. Packing under heat and pressure gets so hard 
that it cuts like a file when left in the stuffing box, and as one 
begins to leak all the old stuff should be pulled out and new put 
in its place. 



Fig. 2. 




THE TRAVEL OF A SIDE VALVE. 

The travel of a slide valve is found as follows : The maximum 
port opening at the head end, plus the maximum port opening at 
the crank end, plus the lap at the head end, plus the lap at the 



crank end. Therefore — 1|" + 1|" 



|"=4i", the re- 



quired travel of valve. Incidentally, it may be well to mention 
that the travel of a valve may also be obtained from the eccentric, 
by subtracting the thin jDart of the eccentric from the thick 
part as per Fig. 1, or again, by taking twice the distance between 
the center of rotation and center of the eccentric. This distance 
on the eccentric is the end valve travel, and is termed the " throw " 
of the eccentric. In the above question, the travel may also be 



HANDBOOK ON ENGINEEJ^ING. 



391 



found by the aid of the diagram, Fig. 2, which is explained as 
follows; From the centered, with a radius of J inch (lap), 
describe a circle BCD, From any point in the circumference, 
say 5, lay off the distance B E equal to the maximum port open- 
ing, If" ; from the center A^ with a radius A E, describe the 
circle E F O; the diameter of the circle E F G is equal to the 
travel of the valve, which is 4i". Let the readers try this with 
another set" of figures, to prove the correctness of the diagram. 

LOSS OF HEAT FROM UNCOVERED STEAM PIPES. 

The following table shows the loss of heat through naked steam 
pipes, wrought iron, of standard sizes. The best covering for a 
steam pipe is hair felt from one to two inches thick, depending on 
the diameter of the pipe, say one inch thick for pipe from 1 to 4 
inches in diameter, and two inches or more for larger pipes. 
Such covering will save at least 96 per cent. Cheaper coverings 
will save from 75 to 90 per cent. The chief value of the table is 
as an aid in estimating the saving that can be made by covering 
the pipe. The money loss by naked pipe being known, the sav- 
ing can be estimated and the cost of the covering will decide its 
value as an investment. 

TABLE OF MONEY LOSS FKOM 100 FEET OF NAKED STEAM PIPE, FOR 
ONE YEAR OF 3000 WORKING HOURS. 





STEAM PRESSURES. 


ssfl 


50 


60 


70 


80 


90 


100 


;ziS^.= 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


1 


113.15 


113.70 


$14.20 


fl4.66 


$15.08 


$15.47 


IV 


• 16.58 


17.29 


17.92 


18.49 


19.02 


19.51 


li 


18.98 


19.78 


20.51 


21.17 


21.77 


22.33 


2 


28.72 


24.73 


25.63 


26.45 


27.21 


27.91 


2h 


28.72 


29.94 


31.03 


32.03 


32.94 


33.79 


3 


34.97 


36.45 


37.78 


38.99 


40.10 


41.14 


4 


44.96 


46.86 


48.57 


50 13 


51.56 


52.89 


5 


55.57 


57.92 


60.04 


61.96 


63.73 


65.38 


6 


66.27 


69.08 


71.60 


73.89 


76.01 


77.96 



392 HANDBOOK ON ENGINEERING. 

RULES AND PROBLEMS APPERTAINING TO THE STEAM 
ENGINE. 

To find the H. P. of a simple non-condensing engine : — 

Rule^ — -Multiply the net area of the piston in square inches, 
by the mean effective pressure in pounds per square inch, and by 
the velocity of the piston in feet per minute, and divide the last 
product by 33,000. The quotient will be the gross H. P. Sub- 
tract from this from ten to twenty per cent for friction in the 
engine itself, and the remainder will be the delivered H. P. 

Example* — The area of the piston is 500 sqr. ins. Half the 
area of the piston-rod is 5 sqr. ins. The M. E. P. is 50 lbs. 
per sqr. in. The stroke is 3 feet, and the revolutions per minute 
125. The friction is 10 per cent. What is the delivered H. P. 
of the engine? Ans. 506.25 H. P. 

Operation* — 3 ft. X 2 = 6 ft. twice the stroke. 

Then, 500 — 5 = 495 sqro ins. net area of piston. 

And, 125 X 6 = 750 ft. the piston speed per minute. 

495X^0X^5^^562.5. 
33,000 

Then, 562.5 X .90 = 506.25. The delivered H. P. 

For a condensing engine: — Add the vacuum to the M. E. P. 
and proceed as above. 

The M. E. P. is the average pressure in the cylinder, less the 
back pressure. 

To find the H. P. of a compound noncondensing engine : — 

The usual method of calculating the H. P. of a multiple cyl- 
inder engine is to assume that all the work is done in the low 
pressure cylinder alone, and that such a M. E. P. is obtained in 
that cylinder as will give the same H. P. as is given by the whole 
engine. 

Rule* — Find the ratio of areas of the high and low pressure 
cylinders, — when of the same stroke, as they usually are, — and 



HANDBOOK ON ENGINEERING. 393 

multiply it by the number of expansions in the high pressure 
cylinder, for the total number of expansions in both cylinders. 
Find the hyperbolic logarithm corresponding to this result and 
add 1 to it, and divide the sum by the total number of expan- 
sions. Multiply this result by the absolute steam pressure, and 
subtract the back pressure. Subtract again the loss in pressure 
between cylinders, and the remainder will be the M. E. P. Then 
multiply the net area of the low pressure cylinder by this M. E. P. 
and by the piston speed in feet per minute and divide by 33,000. 
Deduct the friction in the engine itself and the remainder will be 
the delivered H. P. 

Example* — Given a tandem compound engine with cylinders 
20" and 32" diameter, and 4 feet stroke, making 75 revolutions 
per minute, boiler gauge pressure 125 lbs. per sqr. in., J- cut-off 
in high pressure cylinder, back pressure 15 J lbs. per sqr. in., 
drop in pressure between cylinders 15 per cent, and friction in 
engine 10 per cent. What is the H. P. delivered of this engine? 
Ans. 338.4 H. P. 

Operation* — Neglecting the areas of the piston rods, we 
have : — 

20 X 20 X .7854 — 314.16 sqr. ins. area of high pressure 
cylinder. 

And, 32 X 32 X .7854 = 804„2 sqr. ins. area of low pressure 
cylinder. 

Then, 804.2 -j- 314.16 = 2.56 = the ratio between cylinders. 

And, 2.56X4:^10. 24 = the total number of expansions. 
The hyperbolic logarithm of 10.24 = 2.328. (Seetableonp. 397.) 

And, 1 + 2.328 rzrr 3.328. 

Then, 3.328 -J- 10.24 = .325. 

Also, 125 -f 15 = 140 lbs., the absolute pressure. 

And, .325 X 140 =45.5 lbs., forward pressure. 

And, 45.5 — 15.25 = 30.25 lbs., the M. E. P. 



394 HANDBOOK ON ENGINEERING. 

And, 30.25 X .85 = 25.7 lbs. =the M. E. P. less the 

" drop." 

^,, 804.2 X 25.7 X 8 X 75 .,^,. ^ ^ , 

Then, — — — — — = 376 H. P. nearly. 

33,000 "^ 

And, 376 X .90 = 338.4 H. P. delivered. 

For a compound condensing engine, proceed as above, except 
that the condenser pressure, due to impaired vacuum, only should 
be subtracted from the forward pressure. 

To find the linear expansion of a wrought-iron i3ipe or bar : — 

Rule* — Multiply the length of the pipe or bar m inches by 
the increase in temperature, and by the constant number .0007, 
and divide the last product by 100. 

Example* — G-iven a 6 inch wrought-iron pipe 75 feet long. 
Steam pressure 150 lbs. by gauge. Temperature of pipe when 
put up 60 degs. Fah. What is its linear expansion.? Ans. 
2 ins. nearly. 

Operation* — The diameter of the pipe cuts no figure. 

Then, 150 lbs. pressure = 366 degs. 

And, 366 — 60 = 306 degs. 

Also, 75 X 12 = 900 inches length of pipe. 

^, 306 X 900 X .0007 , ^^^^ . ^ 
Then, 1^ — -^ = 1.9278 mch. 

For copper, use the constant number .0009 ; for brass, use 
.00107 ; for fire-brick, use .0003, and proceed as above. 

To find the proper diameter of steam pipe for an engine : — 

The velocity of steam flowing to an engine should not exceed 
6,000 feet per minute. 

Rule* — Multiply the area of thepiston in square inches by the 
piston speed in feet per minute, and divide by 6,000 ; and divide 
again by .7854, and extract the square root for the diameter of the 
pipe and take the nearest commercial size. 

Example*— Given a 20" X 48" Corliss engine making 72 revo- 
lutions per minute. What should be the diameter of its steam 
pipe? Ans. 6 inches. 



HANDBOOK ON ENGINEERING. S95 



Operation* — 20 X 20 X .7854 =314.16 sqr. ins. 
And, ^^" X 2 X 72 ^ .^^ ^^ ^^^ ^.^^^^ ^p^^^^ 

And. ^-H:li2<^^ =30.15. 
6,000 



Then, ^2ll^ = 6.1". Take 6" pipe. 



\ 



.7854 
To find the water consumption of asteam engine : — 

The most reliable method for determining this, is to make an 
evaporation test, that is, to measure the water fed to the boiler in 
a given time and delivered to the engine in the form of steam. 
But as this method entails considerable trouble and expense, it is 
frequently figured from indicator diagrams. This plan, however, 
does not insure correct results, because the amount of water ac- 
counted for by the indicator is considerably less than it should be 
owing to cylinder condensation and leakage, so that it might be 
possible that only 80 per cent of the water passing through the 
cylinder would be accounted for by the indicator. But the cal- 
culation, used in connection with an evaporation test, will reveal 
the extent of the losses caused by cylinder condensation and 
leakage, by deducting the amount of water found by computation 
from the amount of water fed to the boiler while making an 
evaporation test. 

Rule. — Divide the constant number 859,375 by the M. E. P. 
of any indicator card, and divide this quotient by the volume of 
its total terminal pressure, the result will be the theoretical con- 
sumption in pounds of water per horse power per hour. 

The constant number 859,375 is found as follows: — 

Compute the size of an engine that will give just one horse- 
power at one pound M. E. P. per square inch, thus: 

Area of piston equals 412.5 sqr. inches. 

Stroke equals 4 feet, and revolutions per minute equal 10. 



396 



HANDBOOK ON ENGINEERING. 



Then, the piston speed is (4 x 2 X 10) 80 feet per minute. 

412.5X1X80 
^''^' 33,000 — ^• 

To find how much water it would take to run this engine one 
hour, allowing 62 1- lbs. to the cubic foot of water, proceed as 
follows : — 

Twice the stroke equals 96 inches. 
412.5 X 96 



Then, ^ ' ' " equals 22.91666 cubic feet for one revo- 

1728 
lution. 

And, 22.91666 X 10 equals 229.1666 cubic feet for 10 revolu- 
tions, or for one minute. 

Then, 229.1666 X 60 X 62i equals 859,375 lbs. of water used 
per hour. 




Fig. 1 is not an actual indicator card, but answers to illustrate 
the rule. 

A A is the atmospheric line, and from ^ to ^ is the whole 
stroke. 

VV is the vacuum line. 

Points (a) and (6) are equally distant from the vacuum line. 
The point (a) is taken at or very near the point of release. 



HANDBOOK ON ENGINEERING. 



397 



Example. — From the indicator card Fig. 1 compute the water 
consumption, the M. E. P. being 37.6 lbs. per square inch, the 
scale of spring used in the indicator being 40, the distance from 
point (a) to point (6) being 3.03 inches, the stroke A A being 
3.45 inches, and the pressure at point (a) being 25 lbs. per sqr. 
inch absolute. Ans. 20.14 lbs. 

Operation.— 859,375 ~ 37.6 = 22,855.7. 

Now, the absolute pressure at point (a) is 25 lbs., and steam 
tables give 996 as the volume of steam at this pressure, that is, 
steam at this pressure has 996 times the bulk of the water from 
which it was generated. 

Then, 22,855.7-^-996=22.94 lbs. of water. But as the 
period of consumption is represented by (6) (a), AA being the 
whole stroke, the following correction is required : The distance 
from point (a) to point (6) is 3.03 ins. Then, 22.94 X 3.03 = 
69.5080. And the whole stroke or length of line AA is 3.45 
ins. 

Then, 69.5080 -f- 3.45 = 20.14 lbs. of water per indicated 
horse power per hour. 

TABLE OF HYPERBOLIC LOGAKITHMS. 



NO. 


LOGARITHM. 


NO. 


LOGARITHM. 


NO. 


LOGARITHM. 


1.25 


.22314 


5. 


1.60943 


9.5 


2.25129 


1.5 


.40546 


5.25 


1.65822 


10. 


2.30258 


1.75 


.55961 


5.5 


1.70474 


10.24 


2.328 


2. 


.69314 


5.75 


1.74917 


11. 


2.39789 


2.25 


.81093 


6. 


1.79175 


12. 


2.48490 


2.5 


.91629 


6.25 


1.83258 


13. 


2.56494 


2.75 


1.01160 


6.5 


1.87180 


14. 


2.63905 


3. 


1.09861 


6.75 


1.90954 


15. 


2.70805 


3.25 


1.17865 


7. 


1.94591 


16. 


2.77258 


3.5 


1.25276 


7.25 


1.98100 


17. 


2.83421 


3.75 


1.32175 


7.5 


2.01490 


18. 


2.89037 


4. 


1.38629 


7.75 


2.04769 


19. 


2.94443 


4.25 


1.44691 


8. 


2.07944 


20. 


2.99573 


4.5 


1.50507 


8.5 


2.14006 


21. 


3.04452 


4.75 


1.55814 


9. 


2.19722 


22. 


3.09104 



398 HANDBOOK ON ENGINEERING. 

THE STEAM BOILER. 

CHAPTER XVI. 

THE FORCE OF STEAM AND WHERE IT COMES FROH. 

If water be heated it will expand somewhat, and will finally 
burst forth into vapor. The vapor will expand enormously, and 
naturally occupy more space than the water from which it is 
formed. A cubic inch of water will make a cubic foot of steam ; 
that is, the water has been expanded by heat to seventeen hundred 
times its original bulk. The steam is very elastic ; the water was 
not. When we say that a cubic inch of water will form a cubic 
foot of steam, we mean that it will do so when the steam is allowed 
to rise naturally from the water without any confinement. If the 
steam is confined, as it would be in a boiler, it could not expand, 
and consequently would not. If the steam is allowed to rise into the 
atmosphere from an open vessel, the pressure of the steam would be 
precisely the same as the pressure of the atmosphere, that pressure 
being about fifteen pounds to the square inch. An ordinary steam 
gauge only takes notice of the pressure above the atmospheric 
pressure. When the hand of the steam gauge stands at zero, it 
indicates that there is no pressure above the ordinary pressure of 
the atmosphere. An ordinary steam gauge not connected with 
anything has the atmosphere acting upon it in both directions, the 
same as the atmosphere acts upon everything when it can reach 
both sides. If the air be pumped out of the steam gauge, the 
atmosphere will then act upon one side, and the hand will move 
backward until it stands at fifteen points less than nothing. In 
this condition the steam gauge indicates the absolute zero of 
pressure. If now the air be allowed to re-enter where it was 
pumped out, it will begin to exert its pressure upon the steam 



HANDBOOK ON ENGINEERING. 399 

gauge, and the hand will move forward ; when the full air 
pressure is on, the gauge hand will stand at its usual zero. 
To g"o into this matter in order that it may be understood 
that the real pressure of steam is always fifteen pounds greater 
than ordinary steam gauges indicate. In all of the finer cal- 
culations relating to the action of steam, its total pressure must 
be known, and this total pressure is to be counted from the 
absolute zero. The real pressure of steam is always the steam 
gauge pressure, plus fifeeen pounds. When a steam gauge shows 
fifty pounds, the steam really has a pressure of sixty-five pounds. 
The fifteen jjounds of this pressure is nullified by the atmospheric 
pressure, and the steam gauge shows us our useful pressure. As 
before stated, a cubic inch of water will make a cubic foot of 
steam at atmospheric pressure ; that is, fifteen pounds to the 
square inch, abolute pressure, or zero by the steam gauge. If 
this cubic inch of water was made into steam in a boiler holding 
just a cubic foot, the steam gauge would show zero. If the boiler 
was only large enough to hold half a cubic foot, the steam would 
all be in the boiler, and being confined in half its natural space, 
it would have double pressure. It would have an absolute jjres- 
sure of thirty pounds to the square inch, and the steam gauge 
would indicate fifteen pounds. If this steam was then allowed to 
pass into a chamber holding a cubic foot, the steam would expand 
until it fiUed the chamber, and its pressure would go dov/n again 
to fifteen pounds absolute. In short, the pressure is in reverse 
proportion to the amount of space it occupies. The pressure of 
steam may be doubled bj' compressing the steam into 
one-half its former volume, and so on. After water is 
turned into steam, the steam may be made hotter, but 
it is not very much expanded. The pressure of steam 
is increased by forcing more steam into the space occupied. 
If a boiler contains steam at 50 lbs. pressure, we may increase 
the pressure by adding more steam, and thus compressing all the 



400 HANDBOOK ON ENGINEERING. 

steam that the boiler contains. In the ordinary operation of a 
steam boiler, the fire turns the water into steam and the more 
steam there is made and confined, the greater the pressure will 
be. If the steam is constantly flowing out of the boiler into an 
engine, the pressure in the boiler must be kept up by continually 
making new steam to take the place of that drawn off. If we 
make steam as fast as it is drawn off, and no faster, the pressure 
will remain the same. If we make steam faster than the engine 
draws it off, the pressure will rise, and if it is drawn off faster 
than we make it, the pressure will go down. 

The pressure of the steam is due to its desire to expand into a 
larger body, and it acts outwardly in every direction against 
everything upon which it presses. If we crowd 600 cu. ft. of 
steam in a boiler, which will only hold 100 cu. ft., the steam will 
be held compressed into one-sixth its natural bulk, and will thus 
have a pressure of 90 lbs., and the steam gauge will show 75 lbs. 
If a hole 1 in. square be cut in the boiler, and a weight of 75 lbs. 
be laid over the hole, the steam will just lift the weight. If the 
atmospheric pressure could be removed from one sq. in. of the 
top of the weight, the steam would then be capable of lifting a 
90 lb. weight. The force which this steam will exert to lift a 
weight, or any similar thing against which it acts, will equal the 
pressure per square inch multiplied by the number of square 
inches which the steam acts upon. It will thus be readily under- 
stood that if we lead a pipe from the boiler and fit a piston in the 
pipe, the steam will tend to force this piston out of the pipe. 

THE ENERGY STORED IN STEAM BOILERS. 

A steam boiler is not only an apparatus by means of which the 
potential energy of chemical ajffinity is rendered actual and avail- 
able, but it is also a storage reservoir, or a magazine, in which a 
quantity of such energy is temporarily held ; and this quantity, 



HANDBOOK ON ENGINEERING. 401 

always enormous, is directly proportional to the weight of water 
and of steam which the boiler at the time contains. The energy 
of gunpowder is somewhat variable, but a cubic foot of heated 
water under a pressure of 60 or 70 lbs. per square inch, has about 
the same energy as one pound of gunpowder ; at a low red heat, 
it has about forty times this amount of energy. 

The letters B. T. U. are the initial letters of the words British 
Thermal Unit, and are used as abbreviations of those words. 
The British Thermal Unit is the unit of heat used in this country 
and England, and may be said to be the amount of heat required 
to raise the temperature of one pound of pure water from 60 to 61 
degrees Fahr. It is often necessary to distinguish between 
B. T. U. used in this country and the French thermal unit used in 
France and most of the countries of Europe. The French ther- 
mal unit is:called the calorie, and is the heat required to raise the 
temperature of one kilogram of water one degree centigrade. 

Safety at high pressure depends entirely upon the design, 
material, and workmanship, and it is a question that may be re- 
garded as settled long since, that a steam boiler properly con- 
structed and designed for a working pressure of 150 pounds is as 
safe as a properly constructed boiler designed for eighty pounds, 
with the chances in favor of the high pressure, for the reason that 
less care is taken in selecting boilers for the ordinary pressure, as 
anything in the shape of a boiler is regarded, by careless people, 
as good enough for the lower pressures, with which they have 
become so familiar as to become almost too careless. 

SPECIAL HIGH PRESSURE BOILERS. 

The extending use of compound steam engines, which make 
necessary the employment of high steam pressures, calls for steam 
boilers specially designed to successfully operate under working 
pressures ranging from 100 to 160 pounds. These boilers must 
be safe and economical and of such construction as to afford 

26 



402 HANDBOOK ON ENGINEERING. 

access for examination and repair, moderate in first cost and 
maintenance and of simplest possible form. Fortunately, the 
controlling conditions are not difficult to meet, and there are sev- 
eral well-tried and approved types of steam boilers from which to 
make your selection, choice being governed by the space at dis- 
posal, arrangement of plant, kind of fuel and other circum- 
stances. 

TYPES OF BOILERS. 

Four types that are very succesfuUy used, and they represent 
good practice for high pressure work, being respectively the Hori- 
zontal Tubular, and Vertical Fire Box Tubular Boilers. The Fire 
Box Locomotive Tubular Boiler may safely be added to this list 
and gives most excellent satisfaction. 

THE WATER TUBE BOILER. 

Steam boilers must be designed with reference to the pres- 
sure of steam to be carried, and when so designed and constructed 
are quite as safe at one pressure as another, preference being- 
given to the type that is simplest in form and the least liable to 
destruction, not so much by reason of the pressure carried as by 
failure to provide for the strains of expansion and contraction 
within itself. 

HORSE POWER OF BOILERS. 

In determining the proper size or evaporating cajjacity of a 
boiler to supply steam for a given purpose, it is necessary to con- 
sider the number of pounds of dry steam actually required per 
hour at the stated pressure. The standard horse power rating 
for any steam boiler is 34| pounds of water evaporated (made into 
steam) from feed water at 212° per hour. The total pounds 
steam required for your purpose per hour on this basis divided by 
34^ will give the standard boiler horse power required. Manu- 



HANDBOOK ON ENGINEERING. 403 

facturers of steam boilers sometimes rate the horse power of their 
boilers by so many square feet of heating surface per horse power ; 
8 to 15 sq. ft. of heating surface, they figure, equals one horse 
power. This rating does not represent the actual capacity of the 
steam boiler, the only safe guide being the evaporative perform- 
ance in i^ounds of steam from water at 212° to steam at 212°. 
Some boilers will evaporate this with 8 sq. ft., some requiring 
from 15 to 18 sq. ft., hence, the absurdity of rating horse power 
of boilers of unlike construction by the square feet of heating- 
surface. But as the practice is an old one in the case of the 
well-known tubular boiler, so deservedly popular and used more 
than Siuy other kind, good practice is to allow approximately as 
follows : — 

Allow for each Horse Power - — 

Steam for Heating, etc 15 sq. ft. heating surface. 

For Plain Throttle Engine, ... 15 " " " 

For Simple Corliss Engine . . . 12 " " . " 

For Compound Corliss Condensing .10 " " " 

Hence, a boiler for heating purposes or furnishing steam for — 

Plain Slide engine with 1,500 sq. ft. surface, equals . 100 H. P. 
For Simple Corliss Engine, same boiler " . 125 H. P. 

For Compound Engine '^ . 150 H. P. 

The best method is to compare boilers with their evaporative 
efficiency and not by heating surface. 

The following is an approximate consumption of steam per 
indicated horse power per hour for engine : — 

Plain Slide Engine 60 to 70 pounds. 

High Speed Automatic Engine 30 to 50 " 

Simple Corliss Engine 25 to 35 " 

Compound Corliss Engine 15 to 20 " 

Triple Expansion Engine 13 to 17 " 



404 HANDBOOK ON ENGINEERING. 

depending upon the horse power, steam })ressure, condition of 
engine, load, etc. 

Each pound of first-class steam coal consumed under a well- 
proportioned steam boiler, well managed, should evaporate 10 
pounds of steam from water 212° to steam at 212°. The average 
boiler throughout the country, with ordinary fuel and manage- 
ment, ranges from 5 to 8 pounds steam per pound of coal, and it 
would scarcely be safe to make fuel guarantees per horse power 
of engine without a counter guarantee on the part of the pur- 
chaser, wiien his old boiler is used, that the fuel economy is based 
on an .evaporative efficiency of a given pounds water evaporated 
per pound of coal per hour of his boiler. The usual practice is 
to ignore the boiler altogether and guarantee pounds of steam 
per indicated horse power per hour used by the engine. This 
affords an exact method and is not hampered by unknown con- 
ditions and places all tests on an equal or comparative basis. 

IHE RATING OF BOILERS. 

It is considered usually advisable to assume a set of practically 
attainable conditions in average good practice, and to take the 
power so obtainable as the measure of the power of the boiler in 
commercial and engineering transactions. The unit generally 
assumed has been usually the weight of steam demanded per horse 
power per hour by a fairly good steam engine. In the time of 
Watt, one cubic foot of water per hour was thought fair ; at the 
middle of the present century, ten pounds of coal was a usual 
figure, and five pounds, commonly equivalent to about 40 lbs. of 
feed water evaporated, was allowed the best engines. After the 
introduction of the modern forms of engine, this last figure was 
reduced 25 per cent, and the most recent improvements have still 
further lessened the consumption of fuel and of steam. By general 
consent the unit has now become thirty pounds of dry steam per 



HANDBOOK ON ENGINEERTNO. 40f) 

horse power per hour, which represents the performance of non- 
condensing engines. Large engines, with condensers and com- 
pound cylinders, will do still better. A committee of the 
American Society of Mechanical Engineers recommended thirty 
pounds as the unit of boiler power, and this is now generally 
accepted. They advised that the commercial horse power be 
taken as an evaporation of 30 lbs. of water per hour from a feed 
water temperature of 100° Fahr. into steam at 70 lbs. gauge pres- 
sure, which may be considered equal to 34 J lbs. of water evapo- 
ration, that is, 341 lbs. of water evaporated from a feed water 
temperature of 212° Fahr. into steam at the same temperature. 
This standard is equal to 33,305 British thermal units per hour. 
A boiler rated at any stated power should be capable of 
developing that power with easy firing, moderate draught and 
ordinary fuel, while exhibiting good economy, and at least 
one-third more than its rated power to meet emergencies. 

WORKING CAPACITY OF BOILERS. 

The capacity or horse-power of a boiler, as rated for purposes 
of the trade, is commonly based upon the extent of heating 
surface which it contains. The ordinary rating was for a long 
time 15 sq. ft. of surface per horse-power. At the present time 
most of the stationary boilers are sold on the basis of from 10 to 
12 sq. ft. per horse-power, the power referred to being the unit 
of 30 lbs. evaporation per hour. This method of rating is arbi- 
trary, inasmuch as it is independent of any condition pertaining 
to the practical work of the boiler. The fact that 10 or 12 sq. 
ft. of surface is sold for one horse-power is no guarantee that this 
extent of surface will have a capacity of one horse-power when 
the boiler is installed and set to work. The boiler in service 
and the boiler in the shop are two entirely different things, and 
where one passes to the other, the trade rating disappears. New 



40(i HANDBOOK ON ENGINEERING. 

conditions, such as draft, grate surface, kind of fuel and man- 
agement, then take effect, and these have a controlling influence 
upon the working capacity. The working power may be found 
to be much less than the arbitrary rate, or it may be a much 
larger quantity ; all depending upon the surrounding conditions. 
I call attention to this subject, because it is important in some 
cases to have a clearer understanding as to what is the working- 
capacity of a boiler. Suppose a boiler manufacturer enters into 
an agreement to install a boiler which will have a capacity of 100 
horse-power. Suppose that on account of poor draft, low grade 
of fuel, or unfavorable surroundings, all of which are known 
beforehand, the boiler develops the power named only with the 
most careful handling. Is the working capacity, under the cir- 
cumstances, 100 horse-power? Assuredly not, for the purchaser 
could not depend upon it in ordinary running for that amount of 
power. Yet the builder may claim that he has fulfilled his 
contract. 

The former boiler test committee of the American Society of 
Mechanical Engineers established a working rate for boiler capac- 
ity which meets such cases in a definite and satisfactory manner. 
They realized that for the purpose of good work, a boiler should 
be capable of developing its capacity with a moderate draft and 
easy firing ; and that it should be capable of doing one-third more 
in cases of emergency. In other words, a boiler which is sold 
for 100 horse-power should develop 133i horse-power under con- 
ditions giving a maximum capacity. In the instance cited above, 
the boiler should have been capable of giving 100 horse-power 
with such ease that there would be a reserve of o3i horse-power 
available when urged to this extra power. According to this 
rule, the capacity of a boiler in a working plant would be found 
by determining how much water it can evaporate under conditions 
which will give its maximum capacity; that is, with w^'de open 
damper, with the maximum draft available and with the best con- 



HANDBOOK ON ENGINEERING. 407 

ditions as to the handling of the fire, and in this way ascertain 
the maximum power available under these circumstances. Hav- 
ing found this maximum quantit}^, the working capacit}^ or the 
rated power would be determined by deducting from the maxi- 
mum 25 per cent. This rule, it will be seen, does not take into 
account the extent of the heating surface or the trade rating, but 
it deals solely with the capabilities of the boiler under the con- 
ditions which pertain to its work. 

CODE OF RULES FOR BOILER TESTS. 

Startingf and stopping a test^ — A test should last at least 
ten hours of continuous running, and twenty-four hours whenever 
practicable. The conditions of the boiler and furnace in all 
respects should be, as nearly as possible, the same at the end 
as at the beginning of the test. The steam pressure should be 
the same ; the water level the same ; the fire upon the grates 
should be the same in quantity and condition ; and the walls, flues, 
etc., should be of the same temperature. To secure as near an 
approximation to exact conformity as possible in conditions of 
the fire and in the temperature of the walls and flues, the follow- 
ing method of starting and stopping a test should be adopted : — 

Standard method* — Steam being raised to the working i3res- 
sure, remove rapidly all the fire from the grate, close the damper, 
clean the ash-pit, and, as quickly as possible, start a new fire with 
weighed wood and coal, noting the time of starting the test and 
the height of the water level while the water is in a quiescent 
state, just before lighting the fire. At the end of the test, re- 
move the whole fire, clean the grates and ash-pit, and note the 
water-level when the water is in a quiescent state ; record the time 
of hauling the fire as the end of the test. The water-level should 
be as nearly as possible the same as at the beginning of the test. 
If it is not the same, a correction should be made b}' computa- 



408 HANDBOOK ON ENGINEERING. 

tion, and not by operating pump after test is completed. It will 
generally be necessary to regulate the discharge of steam from the 
boiler tested by means of the stop-valve for a time while fires are 
being hauled at the beginning and at the end of the test, in order 
to keep the steam pressure in the boiler at those times up to the 
average during the test. 

Alternate method* — Instead of the standard method above 
described, the following may be employed where local conditions 
render it necessary : At the regular time for slicing and cleaning 
fires have them burned rather low, as is usual before cleaning, 
and then thoroughly cleaned ; note the amount of coal left on the 
grate as nearly as it can be estimated ; note the pressure of steam 
and the height of the water-level — which should be at the medium 
height to be carried throughout the test — at the same time ; and 
note this time as the time for starting the test. Fresh coal which 
has been weighed, should now be fired. The ash-pits should be 
thoroughly cleaned at once before starting. Before the end of the 
test the fires should be burned low, just as before the start, and 
the fires cleaned in such a manner as to leave the same amount 
of fire, and in the same condition, on the grates as on the start. 
The water-level and steam pressure should be brought to the same 
point as at the start, and the time of the ending of the test should 
be noted just before fresh coal is fired. 

DURING THE TEST. 

Keep the conditions uniform, — The boiler should be run con- 
tinuously without stopping for meal -times, or for rise or fall of 
pressure of steam due to change of demand for steam. The 
draught being adjusted to the rate of evaporation or combustion 
desired before the test is begun, it should be retained constant 
during the test by means of the damper. If the boiler is not con- 
nected to the same steam-pipe with other boilers, an extra outlet 



HANDBOOK ON ENGINEERING. 409 

for steam with valve in same should be provided, so that in case 
the pressure should rise to that at which the safety valve is set, it 
may be reduced to the desired point by opening the extra outlet, 
without checking the fire. If the boiler is connected to a main 
steam-pipe with other boilers, the safety valve on the boiler being 
tested should be set a few pounds higher than those of the other 
boilers, so that in case of a rise in the pressure the other boilers 
may blow off, and the pressure be reduced by closing their dam- 
pers, allowing the damper of the boiler being tested to remain 
open, and firing as usual. All the conditions should be kept as 
nearly uniform as possible, such as force of draught, pressure of 
steam and height of water. The time of cleaning the fires will 
depend upon the character of the fuel, the rapidity of combustion 
and the kind of grates. When very good coal is used and the 
combustion not too rapid, a ten-hour test may be run without any 
cleaning of the grates, other than just before the beginning and 
just before the end of the test. But in case the grates have to be 
cleaned during the test, the intervals between one cleaning and 
another should be uniform. 

Keeping- the records* — The coal should be weighed and 
delivered to the firemen in equal portions, each suflficient for about 
one hour's run, and a fresh portion should not be delivered until 
the previous one has all been fired. The time required to con- 
sume each portion should be noted, the time being recorded at the 
instant of firing the first of each new portion. It is desirable that 
at the same time the amount of water fed into the boiler should 
be accurately noted and recorded, including the height of the 
water in the boiler, and the average pressure of steam and tem- 
perature of feed during the time. By thus recording the 
amount of water evaporated by successive portions of coal, the 
record of the test may be divided into several divisions, if desired 
at the end of the test, to discover the degree of uniformity of com- 
bustion, evaporation and economy at different stages of the test. 



410 HANDBOOK ON ENGINEERING. 



PRIMING TESTS. 

In all tests in which accuracy of results is important, calori- 
meter tests should be made of the percentage of moisture in the 
steam, or of the degree of superheating. At least ten such 
tests should be made during the trial of the boiler, or so many as 
to reduce the probable average error to less than one per cent, 
and the final records of the boiler tests corrected according to the 
average results of the calorimeter tests. On account of the 
difficulty of securing accuracy in these tests, the greatest care 
should be taken in the measurements of weights and temperatures. 
The thermometers should be accurate to within a tenth of one 
degree, and the scales on which the water is weighed to within 
one-hundredth of a pound. 

ANALYSES OF GASES. 

Measurement of air supply, etc. — In tests for purposes of 
scientific research, in which the determination of all the variables 
entering into the test is desired, certain observations should be 
made which are in general not necessary in tests for commercial 
purposes. These are the measurements of the air supply, the 
determination of its contained moisture, the measurement and 
analysis of the flue gases, the determination of the amount of heat 
lost by radiation, of the amount of infiltration of air through the 
setting, the direct determination by calorimeter experiments of 
the absolute heating value of the fuel, and (by condensation of 
all the steam made by the boiler) of the total heat imparted to 
the water. 

The analysis of the flue gases is an especially valuable 
method of determining the relative value of different methods of 
firing, or of different kinds of furnaces. In making these 
analyses, great care should be taken to prqcure average samples 



HANDBOOK ON ENGINEEHTNG. 



411 



since the composition is apt to vary at different points of tlie tlue, 
and the analyses should be intrusted only to a thoroughly com- 
petent chemist, who is provided with complete and accurate 
apparatus. As the determination of the other variables men- 
tioned above are not likely to be undertaken except by engineers 
of high scientific attainments, and as apparatus for making them 
is likely to be improved in the course of scientific research, it is 
not deemed advisable to include in this code any specific direc- 
tions for making them. 

RECORD OF THE TEST. 

A ''log'' of the test should be kept on properly prepared 
blanks, containing headings as follows : — 





Pressures. 


Temperatures. 


Fuel. 


Feed Water. 


Time. 


i 
i 


B 


bJ3 
P 
oi 
bX) 

1 


s 

M 


g 
O 

2 

•i-k 

o 


6 






s 


a 


S 


o 
o 

































REPORTING THE TRIAL. 

The final results should be recorded upon a properly prepared 
blank, and should include as many of the following items as are 
adapted for the specific object for which the trial is made. The 
items marked with a * may be omitted for ordinary trials, but are 
desirable for comparison with similar data from other sources. 



412 



HA^^DBOOK ON ENGINEERING. 



Resources of the trials of a 

Boiler at . 

To determine 

1. Date of trial hours. 

2. Duration of trial hours. 

DIMENSIONS AND PROPORTIONS. 

3. Grate-surface wide long area Sq. ft. 

4. Water-heating surface Sq. ft. 

5. Superheating surface Sq. ft. 

6. Ratio of water-heating surface to grate- 

surface 

AVERAGE PRESSURES. 

7. Steam pressure in boiler, by gauge . . lbs. 

*8. Absolute steam pressure lbs. 

*9. Atmospheric pressure, per barometer . in. 

10. Force of draught in inches of water . . in. 

AVERAGE TEMPERATURES. 

* 11 . Of external air deg. 

*15. Of fire-room d^g. 

*13. Of steam deg. 

14. Of escaping gases . deg. 

15. Of feed- water deg. 

FUEL. 

16. Total amount of coal consumed . . . lbs. 

17. Moisture in coal per cent. 

18. Dry coal consumed lbs. 

19. Total refuse, dry pounds equals . . . per cent. 

20. Total combustible (dry weight of coal, 

item 18, less refuse, item 19) . . , lbs. 

*21. Dry coal consumed per hour . . . lbs. 

*22. Combustible consumed per hour . . . lbs. 



HANDBOOK ON ENGINEERING. 413 

RESUXTS OF CALORIMETRIC TESTS. 

23. Quality of steam, dry steam being taken 

as unity 

24. Percentage of moisture in steam . . . per cent. 

25. Number of degrees superheated . . . deg. 

WATER. 

26. Total weight of water pumped into boiler 

and apparently evaporated .... lbs. 

27. Water actually evaporated, corrected for 

quality of steam lbs. 

28. Equivalent water evaporated into dry 

steam from and at 212° F lbs. 

*29. Pjquivalent total heat derived from fuel 

inB. T. U B. T. U. 

*30. Equivalent water evaporated in dry 

steam from 212^ F. per hour . . . lbs. 

ECONOMIC EVAPORATION. 

31. Water actually evaporated per pound of 

dry coal, from actual pressure and 

temperature . • lbs. 

32. Equivalent water evaporated per pound 

of dry coal, from 212° F lbs. 

33. Equivalent water evaporated per pound 

of combustible from and at 212° F. . lbs. 

COMMERCIAL EVAPORATION. 

34. Equivalent water evaporated per pound 

of dry coal with one-sixth refuse, at 70 
lbs. gauge pressure, from temperature of 
100° F., equals item tests 33 X. 0.7249 
pounds lbs. 

t Corrected for inequality of water level aud of steam pressure at 
beginning and end of test. 



414 HANDBOOK ON ENGINEERING. 

RATE OF COMBUSTION. 

35. Dry coal actually burned per sq. foot of 
grate-surface per hour 



*36. 
*37. 
*38. 



Consumption of dry 

coal per hour. Coal 

assumed with one- 
sixth refuse. 



Per sq. ft. of grate 

surface ... lbs. 

Per sq. ft. of water 

heating surface . lbs. 

Per sq. foot of least 

area for draught. lbs. 



RATE OF EVAPORATION. 

39. Water evaporated from and at 212° F. per 
square foot of heating surface per hour. 

Per sq. ft. of grate' 



*40. 
*41. 

*42. 



Water evaporated per 
hour from temperature 
of 100° F. into steam 
of 70 lbs. gauge pres- 
sure. 



surface ... lbs. 

Per sq. ft. of heat- 
ing surface . . lbs. 

Per sq. ft. of least 

area for draught. lbs. 



COMMERCIAL HORSE POWER. 

43. On basis of 30 lbs. of water per hour 

evaporated from temperature of 100^ F. 
into steam of 70 lbs. gauge pressure 
(341 lbs. from and at 212°) ... H. P. 

44. Horse-power, builders' rating at 

sq. ft. per horse-power 

45. Per cent developed above or below rating per cent. 

* Note. Items 20^ 22, 33, 34, 36, 37, 38 are of little practical value. 
For if the result proves to be less satisfactury than expected on the 
actual coal, it is easy for an expert fireman to decrease No. 20 by simply 
taking out some partly consumed coal in cleaning fires, and thus make a 
fine showing on that simply ideal or theoretical unit, the '^ pound com- 
bustible." The question at issue is always what can be done with an 
actual coal, not the " assumed coal " of items 34, 36, 37 and 38. 



HANDBOOK ON ENGINEERING. 415 

DEFINITIONS AS APPLIED TO BOILERS AND BOILER 
HATERIALS. 

Cohesion is that quality of the particles of a body which causes 
them to adhere to each other, and to resist being torn apart. 

Curvilinear seams* — The curvilinear seams of a boiler are 
those around the circumference. 

Elasticity is that quality which enables a body to return to its 
original form after having been distorted, or stretched by some 
external force. 

Internal radius* — The internal radius is one-half of the diam- 
eter, less the thickness of the iron. To find the internal radius 
of a boiler, take one-half of the external diameter and substract 
the thickness of the iron. 

Limit of elasticity* — The extent to which any material may be 
stretched without receiving a permanent " set." 

Longitudinal seams* — The seams which are parallel to the 
length of a boiler are called the longitudinal seams. 

Strength is the resistance which a body opposes to a disinte- 
gration or separation of its parts. 

Tensil strength is the absolute resistance which a body makes 
to being torn apart by two forces acting in opposite direc- 
tions. 

Crushing strength is the resistance which a body opposes to 
being battered or flattened down by any weight placed upon it. 

Transverse strength is the resistance to bending or flexure, as 
it is called. 

Torsional strength is the resistance which a body offers to 
any external force which attempts to twist it round. 

Detrusive strength is the resistance which a body offers to 
being clipped or shorn into two parts by such instruments as 
shears or scissors. 

Resilience or toughness is another form of the quality of 



416 HANDBOOK ON ENGINEERING. 

strength ; it indicates that a body will manifest a certain degree 
of flexibility before it can be broken ; hence, that body which 
bends or yields most at the time of fracture is the toughest. 

Working strength. — The term " working strength " implies 
a certain reduction made in the estimate of the strength of ma- 
terials, so that when the instrument or machine is put to use, it 
may be capable of resisting a greater strain than it is expected on 
the average to sustain. 

Safe working pressure, or safe load* — The safe working pres- 
sure of steam-boilers is generally taken as I of the bursting pres- 
sure, whatever that may be. 

Strain in the direction of the grain, means strain in the direc- 
tion in which the iron has been rolled ; and in the process of man- 
ufacturing boiler-plates, the direction in which the fibres of the 
iron are stretched as it passes between the rolls. 

Stress* — By the term " stress " is meant the force which acts 
directh^ upon the particles of any material to separate them. 

HEAT AND STEAM. 

The steam engine is a machine for the conversion of heat into 
power in motion. The heat is generated by the combustion of 
fuel ; the transmission is accomplished through the agency of 
steam ; the power is made available and brought under control by 
means of the engine. 

The effect of heat upon water is to vaporize it, if there be inten- 
sity enough, the heat will, under proper conditions, cause water to 
boil ; the vapor produced by boiling is called steam, and steam 
under pressure is a product which is the end and aim of that por- 
tion of that steam engine known as the boiler and furnace. The 
steam engine then is to be considered as a form of the heat 
engine ; of which the furnace, boiler, and the engine itself are to 
be regarded as separate portions of the same mechanism. 



HANDBOOK ON ENGINEERING. 417 

The conditions demanded upon economic grounds to secure 
the highest efficiency in the steam engine are : — 

1. A proper construction of the furnace so as to secure the 
perfect combustion of fuel. 

2 . The heat generated in the furnace must be transferred to the 
water in the boiler without loss. 

3. The circulation in the boiler must be so comjjlete that the 
heat from the furnace may be quickly and thoroughly diffused 
throughout the whole body of water. 

4. The construction of an engine that will use the steam with- 
out loss of heat, except so much as may be necessary to perform 
work required of the engine. 

5. The recovery of heat from exhaust steam. 

6. The absence of friction and back pressure in the working of 
the engine. 

It is superfluous to say that these conditions are not fulfilled 
in any engine of the present day. At best the combustion of 
fuel is only approximately perfect, the losses being due to several 
causes, among which are, — unburned fuel falling through the 
spaces in the grates and mingling with the ashes. This, with 
some kinds of coal, and improper firing, amounts to a large 
percentage of the furnace waste. It is not possible with any 
present method of setting boilers to transfer all the heat of the 
furnace to the water in the boiler ; nor can there be, for the 
reason that the temperature of the escaping gases must not be 
lower than that of the steam in the boilers, or direct loss will result 
in the radiation of heat from the tubes or flues in the boiler, by 
thus reheating the gases to the steam temperature. If the steam 
pressure is 80 lbs. per square inch above the atmosphere, the cor- 
responding temperature due to this pressure is 324° Fahr. The 
temperature of the escaping gases ought not, therefore, to be less 
than 350° Fahr., where they leave the boiler flues or tubes to pass 
off into the chimney. If the temperature of the furnace be taken 

27 



418 HANDBOOK ON ENGINEERING. 

at 2,000° Fahr., and the escaping gases at 400° Falir., it will be 
seen that one-fifth of the heat generated in the furnace is j^assing 
off without performing work. This is a very great loss, and 
these figures understate, rather than correctly give, the loss from 
this one source. Efforts have been made to utilize the tempera- 
ture of these waste gases by making them heat feed water by 
means of coils, or by that particular disposition of pipes and 
connection known as an economizer. Others have turned it into 
account by making it heat the air supplied the fuel on the grates. 
Any heat so reclaimed is money saved, provided it does not cost 
more to get it than it is worth in coal to generate a similar quan- 
tity of heat. It is doubtful whether the loss in this particular 
direction can be brought below 20 per cent of the fuel burned, at 
least, by any method of saving now known. 

The loss by bad firing and by a bad construction of furnace 
is often a large one. It has been demonstrated experimentally 
that 20 to 30 per cent of fuel can be saved by a proper construc- 
tion and operation of the furnace. The direct causes of loss are, 
too low temperature of furnace for properly burning fuels, espe- 
cially such as are rich in hydro-carbon gases ; or, by the admis- 
sion of too much cold air over or back of the fire ; or, by the 
admission of too little air under the fire so that carbonic oxide gas 
is generated instead of carbonic acid gas, the former being a 
product of incomplete, the latter the product of complete 
combustion. The relative heating powers of fuel burned, resulting 
in the production of either of these two gases being as follows : — 

Heat Units. 
1 pound of carbon burned to carbonic acid gas . . 14,500 
1 pound of carbon burned to carbonic oxide . . . 4,500 



Units of heat lost by burning to carbonic oxide . 10,000 
It will be seen that here is an enormous source of loss, and all 
that is required to prevent it is a proper construction of furnace. 



HANDBOOK ON ENGINEERIN(J . 419 

Smoke is a nuisance which ought to be prohibited by stringent 
legislation. There is no good reason for its polluting presence in 
the atmosphere, defiling everything with which it comes in con- 
tact. Smoke regarded as a source of direct loss is greatly over- 
estimated ; the fact is, the actual amount of coal lost to produce 
smoke is ver}^ trifling. The presence of smoke indicates a low . 
temperature of furnace or combustion chamber ; if the temper- 
ature were sufficiently high and the furnace properly constructed, 
smoke could not be generated. The prevention of smoke is 
easily accomplished, and with it a more economical combustion 
of hydro-carbon fuels. 

Radiation* — A considerable loss of heat occurs by radiation 
from the furnace walls ; this may be prevented in part by making 
the walls hollow, with an air space between. If a force blast is 
used the air may be admitted at the back end of the boiler-setting 
and by passing through between the walls will become heated, 
and if conveyed into the ash pit at a high temperature will greatly 
assist combustion and thus tend to a higher economy. 

Air required. — In regard to the quantity of air required, it 
will vary somewhat with the fuel used, but in general, 12 pounds 
of air are sufficient to completely burn one pound of coal ; prac- 
tically, however, 15 to 25 pounds are furnished, being largely in 
excess of that which the fire can use, and must pass off with the 
gases as a waste product. This surplus air enters cold and 
leaves the furnace heated to the same temperature as that of the 
legitimate and proper products of combustion, and thus directly 
operates to the lowering of the furnace temperature. 

Measurement of heat* — A heat unit is that quantity of heat 
necessary to raise the temperature of one pound of water one 
degree, from 39° to 40° Fahr., this being the temperature of the 
greatest density of water. A thermal unit, a heat unit, or unit 
of heat, all mean the same thing. Experiments have been made 
to determine the mechanical equivalent of a heat unit, and it is 



420 HANDBOOK ON ENGINEERING. 

found to be equal to 772 pounds raised one foot high. This is 
sometimes called "Joule's equivalent," after Dr. Joule, of 
England ; it is also known as the dynamic value of a heat unit. 
Knowing the number of heat units in a pound of coal enables 
us to calculate the amount of work it should perform. Let us 
suppose a pound of coal to be burned to carbonic acid gas, 
and to develop during its combustion 14,000 heat units, then: 
14,000 X 772 equals 10,808,000 foot pounds. 

That is to say, if one pound of coal were burned under the 
above conditions it would have a capacity for doing work repre- 
sented by the lifting of ten millions of pounds one foot high 
against the action of gravity. Suppose this to be done in one 
hour, then we should expect to get from one pound of coal an 
equivalent of 5.45 H. P. It is well known that only a very 
small fraction of such equivalent is secured in the very best 
modern practice. The question is, where does this heat go, 
and why is it so small a portion of it is actually utilized? The 
losses may be accounted for in several ways, and, perhaps, as 
follows : — 

The heat wasted in the chimney .... 25 per cent. 

Through bad firing 10 " 

Heataccountedforbytheengine (not indicated) 10 " 
Heat by exhaust steam . . . . . . . 55 " 

100 per cent. 
This is about 2 pounds of coal per hour per indicated horse 
power, which is regarded as a very high attainment, and is 
seldom reached in ordinary cut-off engines. It requires good 
coal, good firing, and an economical engine to get an indicated 
horse power from two pounds of coal burned per hour. As 
coal varies in quality it is a better plan to deduct the ashes 
and other incombustible matter, and take the net combustible 
as a basis of comparison, The best coal when properly ])urned 



HANDBOOK ON KNGINEKRING. 421 

is capable of evaporating- 15 pounds of water from and at a 
temperature of 212° Fahr. The common evaporation is about 
iialf that amount, and with the best improved furnaces and care- 
ful management, it is seldom that 10 pounds of water is exceeded, 
and is to be regarded as a high rate of evaporation. In experi- 
mental tests, 12 pounds have been reported, but it is doubtful 
whether there is any steam boiler and furnace which is con- 
stantly yielding any such results. 

Circulation of water in ^ boiler is a very important feature to 
secure the highest evaporative results. Other things being equal, 
the boiler which affords the best circulation of water will be found 
to be the most economical in service. Circulation is greatly hin- 
dered in some boilers by having too many tubes ; in others, by 
introducing in the water space of the boiler too many stays and 
making the water spaces too narrow. To secure the highest 
economy there must be thorough circulation from below upwards, 
in the boiler. There is no doubt that a great deal of heat is lost 
because the construction is such as to hinder a free flow of water 
around the tubes and sides of the boiler. 

The construction of an engine that will use steam without loss 
of heat, except so much as ina.j be necessary to perform work 
required of it, is a physical impossibility. Among the sources of 
loss in an engine are : radiation, condensation of steam in un- 
jacketed cylinders, and the enormous loss of heat occasioned by 
exhausting the steam into the atmosphere. 

Radiation is usually classed among the minor losses in a steam 
engine. There is a considerable loss of heat caused by radiation 
from steam boilers and pipes exposed to the atmosphere, and not 
protected by a suitable covering. Much of this heat may be 
saved by employing a non-conducting material as a covering, 
which, though not preventing all radiation, will save enough heat 
to make its application economical. It is well known that some 
bodies conduct and radiate heat less rapidly than others, but it 



i22 HANDBOOK ON ENGINEERING. 

must not be understood that the absolute value of such a cover- 
ing is inversely proportioned to the conducting power of the 
material employed, because, in its application, the outer surface 
is enlarged and the radiation will be going on less actively at any 
given point, but the enlarged surface exposed reduces somewhat 
the apparent gain. 

SELECTION OF A BOILER. 

The selection of a boiler for a jjarticular service will naturally 
suggest the following questions : — 

1. What kind of a boiler shall it be ? 

2. Of what material shall it be made,^ 

3. What size shall it be in order to furnish a certain power? 
In reply to the first question, it is to be expected there will be 

wide differences of opinion, varying with the locality, usage, and 
service for which it is intended. One of the first things to be 
taken into account in the selection of a boiler is the quality of 
water to be used in it for generating steam. If the water is pure, 
then it makes little difference what kind of boiler be selected, so 
far as incrustation affects selection. If the water is hard and 
will deposit scale upon evaporation, then a boiler should be 
selected which will admit of thorough inspection and removal of 
any deposit formed within it. 

For hard water, the ordinary flue boiler will be found a good 
one, as it is favorable to a thorough circulation of water, and 
permits easy access to all parts of it for examination and clean- 
ing. It does not, however, present the extent of heating surface 
for a given space that tubular boilers offer ; but with hard water 
the boiler is quite as economical if kept in good condition. 

The difficulty with tubular boilers when used in connection 
with hard water is that the tubes will in a short time become 
coated with scale ; this prevents the transmission of heat, not 
only, but impairs the circulation of the water around them. 



HANDBOOK ON ENGINEERING. 423 

Both of these are opposed to economy in the fact that it requires 
more coal to generate a given weight of steam in the first case ; 
and second, by reason of deficient circulation the plates over the 
fire are likely to become overheated and burnt and so become 
dangerous ; thus directly contributing to accident or disaster. 

The matter of circulation in boilers is one which should have 
careful attention in making a selection. There is little trouble in 
this regard with any of the ordinary types of boilers so long as 
they are clean and new, and joroperly proportioned. Nor is there 
likely to be any difficulty thereafter if the water is soft and clean. 
Circulation is often seriously impaired by putting in too many 
tubes in a boiler, the effect of which is to so fill up the space that 
the heated particles of water forcing their way upwards from 
below meet with so much resistance that they can hardly over- 
come it, and the result is that a boiler does not furnish from one- 
fourth to one-half as much steam for a given weight of fuel as it 
should, from this very cause. 

Boilers intended for use in distant localities where the facilities 
for repairs are meager or entirely wanting, and fuel low j)riced, 
should be of the simplest description. Cylinder boilers or two- 
flue boilers will perhaps be found most suitable. These are 
largely used by coal miners, blast furnaces, saw mills, and other 
branches of industry, which must, of necessity, be removed from 
the larger towns and engineering work shops. 

In selecting a boiler for a mill of any kind where they burn 
shavings or offal, or any other place in which the fuel is of 
a similar description and the firing irregular, there should be 
large water capacity in the boiler that it may act as a reser- 
voir of power in much the same way that a fly wheel acts as 
a regulator for a steam engine. It is a common notion among 
wood- workers that firing with shavings or light fuel is " easy 
on the boiler." There is abundant reason to doubt this. 
The suddenness and rapidity with which an intense fire is kin- 



424 HANDBOOK ON ENGINEERING. 

died in the furnace, lilling all the furnace space and the tubes with 
flame, and with an intense heat which envelops all within the limits 
of draft opening, continuing thus for a few minutes only, and as 
suddenly going out, can hardly be regarded as the ideal furnace. 
Yet there are thousands of just such furnaces at w^ork, and it is 
altogether probable that little or no change will be made in them 
by this class of manufacturers, at least in the near future. In 
regard to the selection of a boiler for this service, we are brought 
back again to the question of hard or soft water. The decision 
should be largely influenced by this, but whatever type of a boiler 
is selected there should be a surplus of boiler power of at least 20 
per cent, that is, if a 50 horse-jwwer boiler is needed to do the 
Work, put in one of 60 horse-power; this will prevent the fluctua- 
tions of speed in the engine which are sure to follow a reduction of 
boiler pressure. 

This increase in boiler power ought not to be simply that of 
tube surface, but should also include extra water space. The 
reserve power of a boiler is in the water heated up to a temperature 
corresponding to the steam pressure ; when this pressure is 
lowered, the water then gives off steam corresponding to the lower 
pressure ; the more water the more steam ; and in this way the 
water in the boiler stores up heat when overfired, to give it off 
again when the fire is low, and so acts a regulator of pressure, a 
thing that extra tube surface cannot do. This kind of firing is 
apt to induce priming, and for this reason a boiler should be 
selected having a large water surface. Horizontal boilers are, in 
general, to be preferred over vertical ones for mills, because of the 
larger water surface exposed in proportion to the heating surface. 
If a tubular boiler is selected, the water line above the tubes 
should be not higher than two-thirds the diameter of the boiler 
measured from the bottom, and the boiler should be made having 
the upper edge of the top row of tubes at least three inches below 
this ; there should also be a clear space up through the center of 



HANDBOOK ON ENGINEERING. 42;") 

the boiler of sufficieut width to insure n perfect circulation of 
water. 

Horizontal tubular boilers are to be recommended when pure 
soft water is used. They combine at once the qualities of great 
strength without excessive bracing, large heating surface, high 
evaporative capacity without liability to priming, and are conve- 
nient of access for external and internal examination when set in 
the furnace. 

Fire box boilers, or locomotive boilers, as they are commonly 
called, are best adapted for small powers and with a fuel which 
deposits but little soot in the tubes. This kind of boiler is sup- 
plied with portable or agricultural engines and is very well adapted 
for that particular service. In canvassing the desirability of 
this kind of a boiler for stationary use, we must again refer to the 
kind of water to be used in it. If the water is soft and clean 
there is then no particular objection to a boiler of this construc- 
tion being used for small powers ; if the water is hard and will 
form scale, it ought not to be chosen, but a flue boiler selected 
instead. 

Vertical boilers are used in great numbers for small engines, 
heating, etc. They have the merit of being compact and low 
priced. A common defect in the construction of this kind of 
boiler is that too many tubes are put in the head in the fire box, 
thereby preventing a proper circulation of water between them. 
This defect in construction induces priming, with all its attendant 
annoyances and dangers. This style of boiler is not suited to 
hard water, but pure soft water only. These boilers should be 
provided with hand holes above the crown sheet and around the 
bottom of the water legs ; at least three at each place mentioned. 
In regard to the material of which a boiler shall be made there is 
but the simple choice between iron and steel. 

Steel for boilers should not be of too high tensile strength ; 
55,000 to 60,000 pounds tensile strength per square inch makes 



4:26 HANDBOOK ON ENGINEERING. 

the best boilers. If the steel is of too high a grade it will take ii 
temper, and, therefore, is utterly unfit for use in steam boilers ; 
if the steel is of too low tensile strength it is apt to be loose or 
spongy. Among the advantages steel possesses over iron may be 
mentioned the circumstance that it is a practically homogeneous 
material when properly made and rolled, consequently, it is nearly 
as strong in one direction as it is in another. In this respect, 
steel is superior to iron plate of equal thickness, because the latter 
is made up of several pieces of iron welded together and in rolling 
into the plate it becomes fibrous, and thus of unequal strength, 
being greatest in the direction of the fiber, and least, when tested 
across it. 

BOILER TRIMMINGS. 

The common trimmings to a steam boiler are a safety valve, 
feed and blow-off pipe, steam pipe, gauge cocks, glass water gauge 
and steam gauge ; to which may be added a steam drum or dome 
and a mud drum. There are numerous other devices which are 
attached to boilers such as safety gauges, alarms, fusible plugs, 
automatic dampers, etc. ; many of these are very serviceable and 
are well liked by those using them. 

Safety valves should always be large enough to permit the 
escape of all the steam a boiler is capable of making and each 
boiler should have its own safety valve rather than connecting two 
or more boilers together and depending on one valve for the 
whole. The valve and seat should be made of hard gun metal, or 
any other composition that will not rust and stick fast. At one 
time it was quite a common thing to see a brass valve fitted to a 
cast-iron seat ; this is wrong, for the rusting of the iron would fix 
the valve so tightly that the boiler would be in constant danger of 
rupture from over pressure. For stationary boilers the common 
ball and lever safety valves are generally used. For stationary 
boilers it is immaterial whether the safety valve be fitted with a 



HANDBOOK ON ENGINEERING. 427 

lever and weight, or whether it be fitted with a spring. The 
former is the usual manner of loading a safety valve and has but 
few objections. For portable engines and locomotives safety 
valves are loaded with springs, which by suitable adjustment may 
be made to blow off at any desired pressure. 

The following' rule is that enforced by the U. S. Government 
in fixing the area of safety valves for ocean and river service, wlien 
the ordinary lever and weight safety valve is employed : — 

Rule* — When the common safety valve is employed it shall 
have an area of not less than one square inch for each two square 
feet of grate surface. 

Another rule is to multiply the pounds of coal burned per 
hour by 4 ; this product is to be divided by the steam pressure, 
to which a constant number 10 is added. 

Example : What would be the proper area for a safety valve 
for a boiler having a grate surface 5 feet square and burning 12 
pounds of coal per hour per square foot of grate ; the steam 
pressure being 75 pounds per square inch? 

5x5 equal 25 square feet of grate. 

25 X 12 equal 300 lbs. of coal per hour. 

300x4 equal 1200. 

75 plus 10 equal 85 equal steam pressure with 10 added, then 
1200/ 85 equal 14.11 inches area, or 41 inches diameter. 

A feed pipe should be at least twice the area over that which is 
regarded as simply necessary to supply the boiler with water, as 
sediment or scale is likely to form in it, which will materially re- 
duce its area. In localities where the water is hard the feed 
jDipes should be disconnected near the boiler and examined occa- 
sionally to ascertain whether or not scale is forming in them. 

In general^ the sizes of feed pipes leading from the pump 
to the boiler are fixed by the size of tap used by the maker of 
the pump. It is not well to reduce the diameter of the pipe and 
the size should be the same throughout. Care should be exer- 



428 HANDBOOK ON ENGINEERING. 

cised iu putting pipes in place that no strain be brought upon them 
by imperfect fitting, as it is certain to lead to leaky joints at some 
time or other. It is also desirable that the pipes be as short and 
straight as possible. Feed pipes should never be placed under 
ground if it is possible to make any different disposition of them. 
In locating pipes it is desirable to arrange for the expansion of 
the boiler, as well as for that of the pipes themselves. In select- 
ing a pump it should have a much larger capacity than that needed 
to supply the boiler, as there are many things which affect the 
working of a pump, such as a defective suction pipe, leaky valves, 
etc. It is the j^ractice of most manufacturers to give the capacity 
of their pumps in gallons of water delivered per minute, from 
which it is easy to select a suitable size ; but the speed given in 
the tables at which the pump is to run is generally faster than 
that which it is desirable to run them. As a general thing, and 
without referring to any particular maker or design, it is a good 
plan to select a pump having four times the capacity actually 
needed for the boiler ; then the speed may be reduced to half that 
given in the table, and will require less repairs, and will be a more 
satisfactory purchase in the long run. 

In selecting" an injector or inspirator, the size should not 
greatly exceed that actually required to supply the boiler. In 
making the steam connections the pipes should start from the 
steam space of the boiler and should not be branches merely from 
the other steam pipes ; neither should the diameters of the pipes 
be less than that which the instrument calls for. The jjipes 
should be as short and straight as practicable ; abrupt bends 
should always be avoided in the suction pipes. If the water is 
taken from a place in which there are floating particles of wood, 
leaves, etc., a strainer should be used; a large sheet metal box 
with perforated sides, makes a good strainer ; the openings ought 
not too greatly exceed an eighth of an inch in diameter, and should 
be several times the area of the suction pipe. 



HANDBOOK ON ENGINEERING. 421) 

A check valve should be fitted with a valve between it and the 
boiler, so that in the event of its not working satisfactorily it may 
be taken apart, cleaned and replaced without stopping for exami- 
nation or repairs. 

The blow-off pipe should be so arranged that it will entirely 
drain the boiler of water ; it is also a good plan to set a boiler 
with a slight inclination toward the blow-off pipe that it may be 
thoroughly drained ; an inclination of two inches in twenty feet 
works well in practice. The blow-off pipe is usually fitted at the 
back end of the boiler. 

The steam pipe naay be connected at any convenient point on 
the top of the boiler. If the boiler is to furnish steam for an 
engine only, the common practice is to make the diameter of the 
pipe one-fourth that of the cylinder. The steam pipe should be 
as short and straight as possible. If bends are to be introduced 
in steam pipes it is better to have a long curved bend than the 
abrupt right-angle fitting usually employed for the purpose. It 
is also a good plan to provide a stop-valve r xt to the boiler to 
shut off the steam and prevent it condensi^-^ in the steam pipe at 
night, or other long stoppages. 

The gauge cocks should not be less than three in number, and 
may be of any of the various kinds now in the market. For 
stationary boilers, the Mississippi gauge cock is, perhaps, as 
good as any. For portable engines a compression gauge-cock is, 
perhaps, the best. The lower gauge-cock should be at least 
2" above the tubes or crown sheet, the middle 2" above the first 
ordinary water line, the upper 2" above the 2 on 2" to 3", de- 
pending on the size of the boiler. 

A glass water gauge should be provided for each boiler and 
should be so located that the water level in the boiler when at the 
lower end of glass shall be one inch above the top of flue. When 
glass gauges are so fitted the fireman can always tell at a glance 
just how much water he has above the flues or crown sheet ; it 



430 HANDBOOK ON ENGINEERING. 

also permits the easy test of accuracy by trying the gauge-cocks 
with the water at a certain known level. Too much dependence 
must not be placed on the glass water-gauge alone, but should be 
used in connection with the gauge-cocks. 

A steam g'aug'e is a very important appendage to a steam 
boiler, and should be chosen with special reference to accuracy 
and durability. The ordinary gauges now in the market are the 
bent tube and the diaphragm gauges. It matters little which of 
the two kinds is selected, provided it is a good and first-class 
gauge. A steam gauge should be compared with a standard test 
gauge at least once a year, to see that it is correct. The 
importance of this will be fully apparent when it is known that it 
furnishes the only means by which the fireman is to judge of the 
steam pressure in the boiler. A siphon should be attached to 
every gauge, and provision should also be made for draining the 
gauge or siphon, to prevent freezing when steam is off the boiler. 
Neglect of this may endanger the accurate reading of the steam 
gauge and render it useless. 

Steam dome* — This is a reservoir for steam riveted to the 
upper portion of the shell and communicated by a central opening 
with the steam space in the boiler. When this reservoir forms a 
separate fixture and is attached to the boiler by cast or wrought 
iron nozzles, it is then called a steam dram. The latter answers 
all the purposes for stationary boilers that the former does, and 
is to be preferred because of the smaller openings in the shell of 
the boiler. A considerable number of boiler explosions have 
been traced directly to the weakness of the shell, caused by the 
large opening in and imperfect staying of the shell underneath 
the dome. When a dome is employed and has a large hole under- 
neath, the strength of the shell is impaired in two ways: 1. By 
reducing the longitudinal sectional area of shell through the cen- 
ter of opening cut for it, which weakness cannot wholly be made 
good by a strengthening ring around the opening. 2. By causing 



HANDBOOK ON ENGINEERING. 431 

a tension equal to that on the crown area of steam dome, upon 
the annular part of the shell covered by the flange of the dome. 
The weakest part of the boiler shell will be where the distance 
from rivet hole at the base of the dome to edge of plate is least. 
It is difficult, owing to the complex nature of the strains, to form 
a rule whereby to determine how much the strength of the shell 
is impaired by using a dome ; but it is quite apparent from gen- 
eral experience that they are in many cases a source of weakness, 
and the larger the dome connection with the shell, the greater the 
liability to rupture. This tendency to rupture is due to the fact 
that the dome, with its connecting flange, is practically inelastic ; 
that portion of the shell of the boiler covered by the dome is, as 
soon as the pressure is introduced on both sides of the plate, 
simply a curved brace. The pressure of the steam in the boiler 
has a tendency to straighten the shell under the dome and thus 
brings about a series .of complex strains which are not easily rem- 
edied by any system of bracing, so that on the whole it is prefer- 
able to use a small connecting nozzle with a drum above it, rather 
than to rivet a large dome directly to the shell. 

Dry pipe. — This is a pipe having numerous small perforations 
on its upper side, and inserted in the upper part of the steam space 
of the boiler. This pipe does not dry the steam, but acts 
mechanically by separating the steam from the water when the 
latter is in a violent state of agitation, and is liable to be carried 
in bulk toward or into the steam pipe. The object of these numer- 
ous small holes in the pipe is that a small quantity of steam may 
be taken from a large number of openings at one time, and thus 
carried over a larger extent of surface than that afforded by a 
single opening, and by this single device checking the tendency to 
priming. 

Steam boiler furnaces are receiving more attention now than 
]3erhaps ever before. The question of economy of fuel is being 
closely studied, and there is now an effort to save much of the 



432 HANDBOOK ON ENGINEERING. 

heat which had formerly been allowed to go to waste. The main 
thing in furnace construction is to get perfect combustion. With- 
out this there must be of necessity a great loss constantly going 
on. There are some losses which it is difficult to prevent, for 
example — the loss by the admission of too much air in the ash 
pit ; the loss by incomplete combustion ; the loss occasioned by 
the heated gases escaping up the chimney ; the loss by radia- 
tion ; but, chief among these, is that of incomplete combustion. 
To burn a pound of coal requires about twenty-four pounds of air, 
or, say 300 cubic feet. Most boiler settings permit from 200 to 300 
feet to pass through the fire. It is needless to point out the 
great source of loss arising from this one cause alone. This may 
be prevented in a measure by having a suitable damper in the 
chimney, and regulating the flow of escaping gases by it, instead 
of the ash pit doors. If the furnace is so constructed that the 
fuel is imperfectly burned, so that carbonic oxide instead of car- 
bonic acid gas is formed, the loss is very great. This results 
often from too little air supply and too low temperature in the 
furnace. The furnace doors should be provided with an opening 
leading into the space between the door proper and the liner ; 
this opening ought to have a sliding or revolving register by which 
the admission of air may be controlled. By this means, the 
quantity of air admitted above the fire may be adjusted to its 
needs by a little attention on the part of the fireman. The liner 
to the furnace door should have a number of small holes in it, 
rather than a solid plate, with a space around the edges. Great 
care should be exercised in the construction of furnace walls, 
that the materials and workmanship be good throughout. The 
entire structure should be brick. The outer walls may be of 
good hard red brick, but the interior walls, around the furnace 
and bridge wall, should be of fire brick. The best quality of fire 
brick for withstanding an intense heat are very, very strong and 
tenacious ; tlie structure is open and they are free from blacli 



HANDBOOK ON ENGINEERING. 433 

spots, due to sulphuret of irou in the clay ; if well burned they 
will not be very light colored on the outside, and will have a 
clear ring when struck. 

Fire brick should be dipped in a thin mortar made of fire clay, 
rather than in a lime and sand mortar, such as is used in ordinary 
red brickwork. In laying up these portions of a boiler furnace 
requiring fire brick, provision should be made in the original wall 
for replacing the fire brick and without disturbing the outer 
brickwork. 

CARE AND MANAGEMENT OF A BOILER. 

It is not enough that a boiler be of approved design, made of 
the best materials, and put together in the best manner; that it 
have the best furnace and the most approved feed and safety 
apparatus. These are all desirable, and are to be commended, 
but cleanliness and careful management are quite essential to get- 
ting high results, and are also conducive to long use in service. 

Pumps^ — Special attention should be given at all times to the 
feed and safety apparatus ; the pumps should be in good working 
order ; it is preferable that they be independent steam pumps 
rather than pumps driven by the engine, or by a belt ; they should 
])e kept well packed and the valves in good condition . 

Fifing* — Kindle a fire and raise steam slowly; never force a 
fire so long as the water in the boiler is below the boiling point. 
The fire should be of an even height, and of such a thickness as 
will be found best for the particular fuel to be burned, but should 
be no thicker than actualh^ necessary. In regard to the size of 
coal used, that will depend upon circumstances. If anthracite 
coal is used, it should not, for stationary boilers, be larger than 
ordinary stove coal. For bituminous coal, which is always shipped 
in lumps as large as can be conveniently handled, the size will 
vary somewhat in breaking, but it may in general be used in 
larger lumps than anthracite. If the coal is likely to cake in burn- 

28 



434 HANDBOOK ON ENGINEERING. 

ing, the fire should be broken up quite frequently with a slice bar, 
or it will fuse into a large mass in the center of the furnace and 
lower the rate of combustion. If the coal is likely to form a con- 
siderable quantity of clinker, or enough to become troublesome, it 
may be advantageous to increase the grate area and thus lower 
the rate of combustion per square foot of grate, and have a fire of 
less intensity. The fire should be kept free from ashes, and the 
ash pit should be kept clean. Whenever the fire door of a steam 
boiler furnace is opened, the damper should be closed to prevent 
the sudden reduction of temperature underneath, which is likely 
to injure the boiler by contraction, and thus render it likely to 
spring a leak around the riveted joints. Some firemen are very 
careless in this respect, and there is little doubt that many a dis- 
agreeable job of repairing a leaky seam might be prevented by 
this simple precaution. 

Gauge cocks should be used constantly to keep them free from 
any accumulation of sediment. It is a very common practice to 
rely wholly on the indications of the glass water gauge for the 
water level in the boiler. This is all wrong and should be dis- 
continued, if once begun. The glass water gauge serves a very 
useful purpose, but it should not be wholly relied on in practice. 
In using the ordinary gauge cocks, the ear more than the eye, 
detects the water level, and thus acts as a check on the indications 
given by the glass gauge. 

Water gauges should be tested several times during the day to 
see that they are clear, and to keep them free from any sediment 
likely to form around the lower opening to the water in the 
boiler. If this is not attended to, the water gauge is likely to 
indicate a wrong water level and a serious accident may be the 
result. 

Steam or pressure gauges are likely to become set after long- 
use and should be tested at least once, or better still, twice a year 
by a standard gauge known to be correct. They should also be 



HANDBOOK ON ENGINEERING. 435 

tested every few days if the boilers are constantly under steam 
by turning off the steam and allowing the pointer to run back to 
zero. If there are two or more boilers set together in one battery, 
and each boiler has its own steam gauge, and which will, starting 
from the zero point, indicate the same pressure on all the gauges, 
they may be assumed to be correct. 

Blow-off cocks or valves should be examined frequently and 
should never be allowed to leak. In general a cock is to be pre- 
ferred to a valve, but both is safer than one ; if the latter is 
selected it should be some one of the various '• straight- way 
valves," of which there are now several in the market. If the 
cock is a large one, and especially if it has either a cast iron shell 
or plug, it should be taken apart after each cleaning out of the 
boilers, examined, greased with tallow and returned. 

Blowing out* — This should be done at least once a day, 
except in the very rare instances in which water is used that will 
not form a scale. The water should not be let out of a boiler or 
boilers until the furnace is quite cold, as the heat retained in the 
walls is likely to injure an empty boiler directly by overheating 
the plates, and indirectly hy hardening the scale within the 
boiler. Bad effects are likely to follow when a boiler is emptied 
of its water before the side walls have become cool ; but greater 
injury is likely to result when cold water is pumped into an empty 
boiler heated in this manner. The unequal contraction of the 
boiler is likely to produce leaky seams in the shell and to loosen 
the tubes and stays. It is a better plan to allow the boiler to 
remain empty until it is quite cold, or sufficiently reduced in tem- 
perature to permit its being filled without injury. Many boilers 
of good material and workmanship have been ruined by the 
neglect of this simple precaution. 

Fusible plugs should be carefully examined every six months, 
as scale is likely to form over the portion projecting into the 
water space. It is only a question of time when this scale 



436 HANDBOOK ON ENGINEERING. 

would form over the eud of the plug, and thick enough to with- 
stand the pressure of steam and thus fail in the accomplishment of 
the very object for which it was introduced. This applies espe- 
cially to the fusible plugs inserted in the crown sheets of portable 
engine boilers. 

Cleaning tubes. — This should be done every day if bitumin- 
ous coal is used. A portable steam jet will be found an extremely 
useful contrivance which will keep them reasonably clean by blow- 
ing out the loose soot and ashes deposited in the tubes. Every 
two or three days, or at least once a week, a tube scraper or stiff 
brush should be used to take out all the ashes or soot adhering 
to the tubes and which cannot be blown out with the jet. Flues 
may be cleaned the same way but will not require to be done so 
frequently. 

Low water* — : If from any cause the water gets low in the 
boiler, bank the fire with ashes or with fresh coal as quickly as 
possible, shut the damper and ash pit doors and leave the tire 
doors wide open ; do not disturb the running of the engine but 
allow it to use all the steam the boiler is making ; do not 
under an}^ circumstances attempt to force water in the boiler. 
After the steam is all used and the boiler cooled sufficiently to be 
safe, then the water may be admitted and brought up to the reg- 
ular working height ; the damper opened and the fires allowed to 
burn and steam raised as usual; provided, no injury has been 
done the boiler by overheating. 

Foaming and priming are always troublesome and often danger- 
ous. Some boilers prime almost constantly, because of their bad 
proportion, and will require the constant care of the person in 
charge, especially at such times as the engine may be using the 
steam up to the full capacity of the boiler. In a case of this kind, 
an increase in pressure will often check, but will not entirely 
prevent it ; nothing short of an increase of water surface, or a 
better circulation of water, or a larger steam room will afford a 



IIANDIJOOK ON ENG1NEEKIN(4. 437 

complete remedy. If the foaming or priming is due to a sudden 
liberation of steam, or on account of impure feed water it may be 
checked by closing the throttle valve to the engine and opening 
he fire door for a few minutes. The surface blow may be used 
with advantage at this time, by blowing off the impurities collected 
on the surface of the water. The feed pump may be used if 
necessary, but care should be exercised that too much cold water 
be not forced into the boiler, and thus lose time by having to 
wait for the accumulation of the regular steam pressure required 
for the engine. The dangers attending foaming or priming arc r. 
the laying bare of heating surfaces in the boiler, and of breaking 
down the engine by working water into the cylinder. The com- 
monest damage to the engine being either the breaking of a cylin- 
der head, or the cross-head, or the breaking of the piston. Wbeu 
boilers are new and set to work for the first time priming is a very 
frequent occurrence ; in fact, it may be said that for the first few 
days there is always more or less of it. All that is needed during 
this time is a little care on the part of the attendant to see that 
the water is kept up to the required level in the boiler ; it is also 
recommended that the throttle valve to the engine be partially 
closed to prevent any very great variation of pressure in the 
boiler, and thus prevent water passing over with the steam 
in such quantities as to become dangerous. If a boiler 
continues to prime after it has had a weed's work and 
then thoroughly cleaned, the causes are to be attributed to 
other than the grease and dirt in it, which are inseparable from 
the manufacture. As already said, jjriming may be caused by a 
sudden reduction of pressure ; that is, a boiler may be working 
smoothly and well with say 80 pounds pressure ; if an increase 
of load be suddenly applied to an engine so as to reduce the 
pressure to 70 or 60 pounds, this sudden reduction of pressure 
will almost always cause priming ; the less the steam space in the 
boiler, the greater the tendency to prime, and the greater the 



438 HANDBOOK ON ENGINEERING. 

difficulty iu checking it. The only permanent cure for this is 
more boiler power ; as a temporary expedient, the engine should 
be throttled sufficiently to make the drain upon the boiler con- 
stant instead of intermittent. If the duty required of an engine 
is irregular, the steam pressure should be carried higher ; in any 
case similar to the above, it is recommended that the pressure be 
increased to 90 or 100 pounds and the throttling to begin with 
the increased drain upon the boiler. But this is at best a mere 
makeshift, and a larger boiler power becomes imperative both 
on the score of economy and safety. 

WATER FOR USE IN BOILERS. 

Water is never pure, except when made so in a laboratory or 
by distillation ; the impurities may be divided into four classes : 
1. Mechanical impurities. 2. Gaseous impurities. 3. Dissolved 
mineral impurities. 4. Organic impurities. 

(a) Mechanical impurities may be both mineral and organic. 
The commonest suspended impurity in water is mud or sand ; 
these may be removed by filtration or by allowing the water to 
stand long enough to let them settle to the bottom of the tank or 
cistern and then carefully drawing the water from the top, and 
without disturbing the bottom. 

(b) Gaseous impurities in water vary somewhat according to the 
localities from which they are obtained. The commonest gases 
found in the water are an excess of oxygen, nitrogen and carbonic 
acid. These have no effect on water intended for steam boilers. 

(c) Dissolved mineral impurities in water are of the most 
varied description, and are almost always found in it. Among 
these are found salts of iron, sulphate and carbonates of lime ; 
sulphate and carbonates of magnesia; salt and alkalies, such as 
soda, potash, etc. ; acids, such as sulphuric, phosphoric, and 
others. All of these are more or less injurious to steam boilers. 
The most objectionable are the salts of lime and magnesia, which 
impart to water that property known as hardness. When such 



HANDBOOK ON ENGINEERING. 4B9 

water is used in a steam boiler a scale will gradually form, which 
will^ in a short time, become very troublesome. 

(d) Organic impurities are present, to a certain extent, in 
most waters. They are sometimes present in the water in suffi- 
cient quantities to give it a very decided color and taste. 

The presence of organic matter in water is often dangerous to 
health, and may be a means of spreading contagious diseases, 
but has little or no bad effect in any water used for steam boilers. 
In general, water is regarded by engineers as being either soft, 
hard or salt. 

Ebullition* — Is the motion produced in a liquid by its rapid 
conversion into vapor. When heat is applied to the bottom of a 
boiler, the particles of water in contact with the plates become 
heated and immediately expand, and becoming specifically lighter, 
pass upwards through the colder body of water above ; the heat of 
the furnace is in this way diffused throughout the whole body of 
water in the boiler by a translation of the particles of water from 
below upwards, and from top to bottom in regular succession. 
After a time this liquid mass becomes heated to a degree in which 
there is a violent agitation of the whole body of water, steam is 
given off and it is said to boil. The temperature at the boihng 
point of water, at ordinary atmospheric pressure, is 212° Fahr., 
and increases as the pressure of steam above it increases. 

Distilled water for boilers is not to be recommended without 
some reservation. Chemically pure water, and especially water 
which has been redistilled several times, has a corrosive action on 
iron which is often very troublesome. The effect on steel plates 
by the use of water several times redistilled, such, for example, as 
that supplied for heating buildings, is well known ; information is 
yet wanting which shall point with certainty to the exact change 
which the water undergoes and explain why its action on or 
affinity for steel is so greatly intensified. It has been suggested 
as a means of neutralizing this corrosive action of the water, to 



440 HANDBOOK ON ENGINEERING. 

introduce with the feed other water, which shall have the prop- 
erty of forming a scale and continuing it long enough and at such 
intervals as will permit the formation of a thin scale in the interior 
of the boiler. However objectionable this may seem at first 
sight, it is at present the best practical solution of the difficulty. 

Scale is a bad conductor of heat and is opposed to economical 
evaporation. It is estimated that a thickness of half an inch of 
hard scale firmly attached to a boiler plate will require a temper- 
ature of about 700^ Fahr. in the boiler plate in order to raise and 
maintain an ordinary steam pressure of 75 pounds. The mis- 
chievous effects of accumulated scale in the boiler, especially in 
the plates immediately over the fire, are : (1) preventing the water 
from coming in contact with the plates, and thus directly con- 
tributing to the overheating of the latter; and (2) by causing a 
change of structure in the plates and the consequent weakening 
brought about by this continual overheating, which would, in a 
short time, render an iron or a steel plate wholly unfit for use in 
a steam boiler. The two principal ingredients in boiler scale are 
lime and magnesia. The lime, when in combination with 
carbonic acid, forms carbonate of lime ; when in combination with 
sulphuric acid, it then becomes sulphate of lime. This is also 
true of magnesia. 

Carbonate of lime will form in the boiler as a loose powder 
which is held mechanically in suspenion ; while in this stage it 
may be blown out of the boiler without injury to it ; but it is 
seldom that a pure carbonate is formed in the boiler as there are 
other impurities in the water with which it combines to form a 
hard scale. This is especially true in such waters as also contain 
sulphate of lime in solution. This fine powder (carbonate of 
lime), will form a hard scale should any adhere to the sides or 
bottom of a boiler ; in any case where the boiler is blown out dry 
while the furnace walls are still hot ; and this, in itself, forms an 
excellent reason why boilers should stand until the furnace walls 



HANDBOOK ON ENGINEERING. 441 

are cold before blowing out. AVheii emptied, nearly or all of this 
slushy deposit may be washed out of the boiler by means of a 
hose. 

Sulphate of lime is not so easily got rid of, as it is heavier than 
carbonate of lime and adheres to the plates while the boiler is at 
work. It is the most troublesome scale steam engineers have to 
deal with ; it is very difficult to remove and by successive layers 
becomes dangerous, on account of the thickness to which it 
eventually accumulates. 

The carbonates of lime and magnesia may be largely arrested 
by passing the feed water through a suitable heater and lime 
extractor. It must be apparent to every one that any device 
which will accomplish this is a very desirable attachment to a 
steam boiler. As it is not possible to eliminate all the foreign 
matter in the water from it, recourse is often had to the use of 
solvents and chemical agencies for the prevention of scale. Some 
of these are very simple and within easy reach ; others are sur- 
rounded by an atmosphere of uncertainty and the real nature of 
the compound is hidden under a meaningless trade-mark. For 
carbonate of lime, potatoes have been found to be very service- 
able in preventing the formation of scale ; its action appears to 
be that of surrounding the particles of lime with a coating of 
starch and gelatine, and thus preventing the cohesion of these 
particles to form a mass. Various astringents have been used for 
this purpose, such as extracts of oak and hemlock bark, nutgalls, 
catechu, etc., with varying success. 

Carbonate of soda has been used and with very great success in 
some localities, not only in preventing, but in actually removing 
scale already formed. It acts on carbonate of lime not only, but 
on the sulphate also. It is clean, free from grit, and is quite 
unobjectionable in the boiler ; one or more pounds per day, de- 
pending on the size of the boiler, may be admitted through the 
pump with the feed water ; or admitted in the morning before 



442 HANDBOOK ON ENGINEERING. 

tiring up, by simply mixing with water and pouring into the boiler 
through the safety valve or other opening. 

Tannate of soda has been similarly employed and is an excel- 
lent scale preventive. It will also act as a solvent for scale 
already formed in the boiler, acting on sulphate as well as carbon- 
ate of lime. 

Crude petroleum has been found very beneficial in removing 
the hard scale composed principally of sulphate of lime. 

Zinc in steam boilers*^ The employment of zinc in steam 
boilers, like that of soda, has been adopted for two distinct 
objects: (1) to prevent corrosion, and (2) to prevent and 
remove incrustation. To attain the first object, it has been used 
chiefly in marine boilers, and for the second, chiefly in boilers fed 
with fresh water. In order that the application of zinc in marine 
boilers may be effective, it is necessary that the metallic contact 
should be insured. If galvanic action alone is relied upon for the 
protection of the plates and tubes, it will doubtless be diminished 
materially by the coating of oxide that exists between all joints of 
plates, whether lapped or butted, and also between the rivets and 
the plates. Assuming the ]3reservative action of zinc to be proved 
when properly applied, we have now two systems for preventing 
the internal decay of marine boilers, viz. : allowing the plates and 
tubes to become coated with scale, and employing zinc. It 
remains to decide which of these two systems is the best with 
respect to economy and practicability. 

We come now to consider the use of zinc for preventing and 
removing incrustation. 

-At one time it was considered that the action of zinc in pre- 
venting incrustation was physical or mechanical. The particles 
of zinc, as it wasted away, were supposed to become mixed 
amongst the solid matter precipitated from the water, in such a 
manner as to prevent it adhering together, so as to form a hard 
scale ; or the particles of zinc were supposed to become deposited 



HANDBOOK ON ENGINEERING. 443 

upon the plates, and so prevent the scale from adhering to them. 
Then it was suggested that the zinc acted chemically, and now, it 
is the generally received opinion that its action is galvanic in 
preventing incrustation as well as in preventing corrosion. When 
the water contains an excess of sulphates or chlorides over the 
carbonates, the acid of the former will form soluble salts with the 
oxide of zinc, the surface of the zinc will be kept clean, and the 
galvanic current, to which the efficiency of the zinc is due, will be 
maintained. On the other hand, should there be a ijrei3onderat- 
ing amount of carbonates, the zinc will be covered first with oxide, 
then with carbonates and its useful action arrested and stopped. 
It is quite as important that the zinc should be in metallic con- 
tact with the plates when used to prevent incrustation, as when 
employed to prevent corrosion. The application of zinc for the 
former purpose should never be attempted without first having the 
water analyzed in order to ascertain whether it is likely to be 
effective. The use of zinc in externally fired boilers should be 
attempted with great caution, as when efficacious in preventing 
the formation of a hard scale, it is liable to produce a heavy 
sludge that may settle over the furnace plates and lead to over- 
heating. On the whole we cannot but regard the evidence as to 
the effect of zinc upon incrustation as being very conflicting. 

Leaks should be stopped as soon as possible after their dis- 
covery ; the kind of leak will indicate the treatment necessary. 
If it occurs around the ends of the tubes, it may be stopped by 
expanding the tubes anew ; if in a riveted joint, it should be care- 
fully examined, especially along the line of the rivets and care 
should be exercised in determining whether there is a crack 
extending from rivet to rivet along the line of the holes : should 
this prove to be the case, the boiler is then in an extremely 
dangerous condition and under no circumstances should it be 
again fired up until suitable repairs have been made which will 
insure its safety. 



444 HANDBOOK ON ENGINEERING. 

Blisters occur in plates which are made up of several thick- 
nesses of iron and which from some cause were not thoroughly 
welded before the final rolling into plates. When such a plate 
comes in contact with the heat of the furnace the thinnest portion 
of the defective plate " buckles " and forms what is called a 
blister. As soon as discovered, there should be thorough exami- 
nation of the plate and if repairs are needed there should be as 
little delay as possible in making them. If the blister be very 
thin and altogether on the surface it may be chipped and dressed 
around the edges ; if the thickness is equal or exceeds J^" the 
blister should be cut off and patched, or a new plate put in. 

Patching" boilers* — When a boiler requires patching it is bet- 
ter to cut out the defective sheets and rivet in a new one ; or if 
this cannot be done, a new piece large enough to cover the defect 
in the old sheet may be riveted over the hole from which the 
defective portion has been cut. If this occurs in any portion of 
the boilei subject to the action of fire, the lap should be the same 
as the edges of the boiler seams, and should be carefully calked 
around the edges after the riveting. Whenever the blisters occur 
in a plate, patching is a comparatively simple thing as against the 
repairs of a plate worn by corrosion. In the latter case, the 
defective portions of the plate should be entirely removed and the 
openings should show sound metal all around and of full thick- 
ness. If this cannot be obtained within a reasonable sized open- 
ing then the whole plate should be removed. 

It often occurs that a minor defect is found in a plate and at a 
time when it is not convenient to stop for repairs ; in such an 
event a " soft patch " is often applied. This consists of a piece 
of wrought iron carefully fitted to that portion of the boiler plate 
needing repairs ; holes are fitted in both plates and patch, and 
" patch bolts " i^rovided for them. A thick putty consisting of 
white and red lead with iron borings or filings in them placed 
evenly over the inner surface of the patch, which is then tightly 



HANDBOOK ON ENGINEERING. 445 

bolted to the boiler plate. This is best but a temporary make- 
shift and ought never to be regarded as a permanent repair. A 
mistake is often made of making a patch of thicker metal than 
that of the shell of the boiler needing it. A moment's reflection 
ought to show the absurdity of 23utting on a ^^ or | patch on an 
old i inch boiler shell ; yet it is not so rare as one would imagine. 
A piece of new iron -f^" thick will, in most cases, be found to be 
stronger than that portion of a J" old plate needing repairs. 

Inspection* — A careful external and internal examination of a 
boiler is to be commended for many reasons. This should be as 
frequent as possible and thoroughly done ; it should include the 
boiler not only, but all the attachments which affect its working 
or pressure. Particular attention should be paid to the examina- 
tion of all braces and stays, safety valve, pressure gauges, water 
gauges, feed and blow-off apparatus, etc. ; these latter refer more 
particularly to constructive details necessary to proper manage- 
ment and safety. The inspection would obviously be incomplete, 
did it not include an examination into the causes of " wear and 
tear," and determine the extent to which it had progressed. 
Among the several causes which directly tend to rendering a 
boiler unsafe, may be mentioned the dangerous results occasioned 
by the overheating of plates, thus changing the structure of the 
iron from fine granular, or fibrous, to coarse crystalline. This 
may easily be detected by examination, and will in general be 
found to occur in such cases where the boilers are too small for 
the work, are fired too hard, or have a considerable accumulation 
of scale or sediment in contact with the plates. Blistered plates 
are almost instantly detected at sight, so also is corrosion, from 
whatever cause it may have proceeded. 

Cof fosion of boilei* plates* — Iron will corrode rapidly when 
subjected to the intermittent action of moisture and dryness. 
Land boilers are less subject to corrosion than marine boilers. 
The corrosion of a boiler may be either external or internal. Ex- 



446 HANDBOOK ON ENGINEERING. 

ternal corrosion may, in general, be easily prevented by carefully 
caulking all leaks in the boiler ; by preventing the dropping cf 
water on the plates, such, for example, as from a leaky joint in 
the steam pipe or from the safety valve. A leaky roof, by allow- 
ing a continual or occasional dropping of water on the top of a 
boiler, especially if the boiler is not in constant use, would pro= 
mote external corrosion. Sometimes external corrosion is caused 
by the use of coal having sulphur in it, and acts in this way : The 
sulphur passes off from the fire as sulphurous oxide, which often 
attaches to the sides of a boiler ; so long as this is dry no especial 
mischief is done ; but if it comes in contact with a wet plate the 
sulphurous oxide is converted into sulphuric acid over so much 
of the surface as the moisture extends ; this acid attacks, and 
will, in time, entirely destroy the boiler plate. Internal corrosion 
is not so easily accounted for and is very difficult to correct, 
especially when it occurs above the water line. It is generally 
believed to be due to the action of acids in the feed water. 
Marine boilers are especially subject to internal corrosion when 
used in connection with surface condensers. A few years ago it 
was generally supposed to be due to galvanic action but that idea 
is now almost entirely given up. From the fact that boilers using 
distilled water fed into them from surface condensers are more 
liable to internal corrosion than other boilers, has led to the theory 
that it is the pure water that does the mischief, and that a water 
containing in slight degree a scale-forming salt, is to be preferred 
to water which is absolutely pure. Whatever maybe the truth or 
falsity of this theory, it is a well established fact that distilled 
water has a most pernicious action on various metals, especially 
on steel, lead and iron. This action is attributed to its peculiar 
property, as compared with ordinary water, of dissolving free 
carbonic acid. One of the worst features in connection with 
internal corrosion is that its progress cannot be easily traced on 
account of the boiler being closed while at work. As it does not 



HANDBOOK ON ENGINEERING. 447 

usually extend over any very great extent of surface, the ordinary 
hydraulic test fails to reveal the locality of corroded spots ; the 
hammer test, on the contrary, rarely fails to locate them, if the 
plates are much thinned by its action. 

Testing boilers, — It is the general practice to apply the 
hydraulic test to all new steam boilers at the place of manufacture, 
and before shipment. The pressure employed in the test is from 
one and a half to twice the intended working steam pressure. 
This test is only valuable in bringing to notice defects which 
would escape ordinary inspection. It is not to be assumed that 
it in any way assures good workmanship, or material, or. good 
design, or proper proportions ; it simply shows that the boiler 
being tested is able to withstand this pressure without leak- 
ing at the joints, or distorting the shell to an injurious degree. 
Bad workmanship may often be detected at a glance by an expe- 
rienced person. The material must be judged by the tensile 
strength and ductility of the sample tested. The design and pro- 
portions are to be judged on constructive grounds, and have little 
or nothing in common with the hydraulic test. The great majority 
of buyers of steam boilers have but little knowledge on the sub- 
ject of tests, and too often conclude that if they have a certified 
copy of a record showing that a particular boiler withstood a test 
of say, 150 lbs., it is a good and safe boiler at 75 to 100 lbs. 
steam pressure. If the boiler is a new one and by a reputable 
maker, that may be true ; if it has been used and put upon the 
market as a second-hand boiler, it may be anything but safe at 
half the pressure named. By the hydraulic test, the braces in a 
boiler may be broken, joints strained so as to make them leak, 
bolts or pins may be sheared off, or so distorted as to be of little 
or no service in resisting steam when pressure is on. 

Hammer test* — The practice of inspecting boilers by sounding 
with a hammer is, in- many respects, to be commended. It 
requires some practical experience in order to detect blisters and 



448 HANDBOOK ON ENGINEERING. 

the wasting of plates, by sound alone. The hammer test is 
especially applicable to the thorough inspection of old boilers. It 
frequently happens in making a test that a blow of the hand 
hammer will either distort it, or be driven entirely through the 
plate ; and it is just here that the superiority of this method of 
testing over, or in connection with the hydraulic test, becomes 
fully apparent. The location of stays, joints and boiler fittings all 
modify and are apt to mislead the inspector if he depends upon 
sound alone. There is a certain spring of the hammer and a clear 
ring indicative of sound plates, which are wanting in plates much 
corroded or blistered. The presence of scale on the inside of the 
boiler has a modifying action on the sound of the plate. When a 
supposed defect is discovered, a hole should be drilled through 
the sheet by which its thickness may be determined, as well as 
its condition. 



HANDBOOK ON ENGINEERING. 449 



CHAPTER XVII. 

USE AND ABUSE OF THE STEAM=BOILER. 

Steam-boilets* — A steam-boiler may be defined as a close 
vessel, in which steam is generated. It may assume an endless 
variety of forms, and can be constructed of various materials. 
Since the introduction of steam as a motive power a great variety 
of boilers has been designed, tried and abandoned ; while many 
others, having little or no merit as steam generators, they have 
their advocates and are still continued in use. Under such cir- 
cumstances, it is not surprising that quite a variety of opinions 
are held on the subject. This difference of opinion relates not 
only to the form of boiler best adapted to supply the greatest 
quantity of steam with the least expenditure of fuel, but also to 
the dimensions or capacity suitable for an engine of a given num- 
ber of horse-power ; and while great improvements have been 
made in the manufacture of boiler materials within the past 
fifteen years, yet the number of inferior steam-boilers seem to 
increase rather than diminish. It would be difficult to assign any 
reasonable cause for this, except that, of late years, nearly the 
whole attention of theoretical and mechanical engineers has been 
directed to the improvement and perfection of the steam-engine, 
and practical engineers, following the example set by the leaders, 
devote their energies to the same object. This is to be regretted, 
as the construction and application of the steam-boiler, like the 
steam-engine, is deserving of the most thorough and scien- 
tific study, as on the basis of its employment rest some 
of the most important interests of civilization. Until quite 
recently, the idea was very generally entertained that the 
durely mechanical skill required to enable a person to join 

29 



450 HANDBOOK ON ENGINEERING. 

together pieces of metal, and thereby form a steam-tight and 
water-tight vessel of given dimensions, to be used for the gen- 
eration of steam to work an engine, was all that was needed ; 
experience has shown, however, that this is but a small portion ol 
the knowledge that should be possessed by persons who turn theii 
attention to the design and construction of steam-boilers, as the 
knowledge wanted for this end is of a scientific as well as of a 
mechanical nature. As the boiler is the source of power and the 
place where the power to be applied is first generated, and alsc 
the source from which the most dangerous consequences may arise 
from neglect or ignorance, it should attract the special attention 
of the designing and mechanical engineer, as it is well known 
that from the hour it is set to work, it is acted upon by destroy- 
ing forces, more or less uncontrollable in their work of destruc- 
tion. These forces may be distinguished as chemical and 
mechanical. In most cases they operate independently, though 
they are frequently found acting conjointly in bringing about the 
destruction of the boiler, which will be more or less rapid accord- 
ing to circumstances of design, construction, quality of material, 
management, etc. The causes which most affect the integrity of 
boilers and limit their usefulness are either inherent in the mate- 
rial, or due to a want of skill in their construction and manage- 
ment ; they may be enumerated as follows : — 

First, inferior material ; second, slag, sand or cinders being- 
rolled into the iron ; third, want of lamination in the sheets ; 
fourth, the overstretching of the fiber of the plate on one side and 
puckering on the other in the process of rolling, to form the circle 
for the shell of a boiler ; fifth, injuries done the plate in the pro- 
cess of punching ; sixth, damage induced by the use of the drift- 
pin ; seventh, carelessness in rolling the sheets to form the shell, 
as a result of which the seams, instead of fitting each other 
exactly, have in many instances to be drawn together by bolts, 
which aggravates the eyils of expansion and contraction when the 



HANDBOOK ON ENGINEERING. 451 

boiler is in use ; eighth, injury done the plates by a want of skill 
in the use of the hammer in the process of hand-riveting ; ninth, 
damage done in the process of calking. 

Othet causes of deterioration are unequal expansion and con- 
traction , resulting from a want of skill in setting ; grooving in the 
vicinity of the seams ; internal and external corrosion ; blowing 
out the boiler when under a high pressure and filling it again with 
cold water when hot ; allowing the fire to burn too rapidly after 
starting, when the boiler is cold ; ignorance of the use of the pick 
in the process of scaling and cleaning ; incapacity of the safety- 
valve ; excessive firing ; urging or taxing the boiler beyond its 
safe and easy working capacity; allowing the water to become 
low, and thus causing undue expansion ; deposits of scale accum- 
ulating on the parts ex]30sed to the direct action of the fire, 
thereby burning or crystallizing the sheets or shell ; wasting of the 
material by leakage and corrosion ; bad design and construction 
of the different parts ; inferior workmanship and ignorance in the 
care and management. All these tend with unerring certainty to 
limit the age and safety of steam boilers. On account of want of 
skill on the part of the designer and avarice on the part of the 
manufacturer, or perhaps both reasons, boilers are sometimes so 
constructed as to bring a riveted seam directly over the fire, the 
result of which is that in consequence of one lap covering the 
other, the water is prevented from getting to the one nearest the 
fire, for which reason the lap nearest the fire becomes hotter and 
expands to a much greater extent than any other part of the 
plate ; and its constant unequal expansion and contraction, as 
the boiler becomes alternately hot and cold, inevitably results in a 
crack. Such blunders are aggravated by the scale and sediment 
being retained on the inside, between the heads of the rivets, 
which should be properly removed in cleaning. 

The tendency of manufacturers to work boilers beyond their 
capacity, especially when business is driving, is too great in this 



452 HANDBOOK ON ENGINEERING. 

country ; and no doubt many boiler explosions may be attributed 
to this cause. Boilers are bought, adapted to the wants of the 
manufactory at the time, but, as business increases, machinery 
is added to supply the demand for goods, until the engine is 
overtasked, the boiler strained and rendered positively danger- 
ous. Then again, it not unfrequently occurs that engines in 
manufactories are taken out and replaced by those of increased 
power, while the boilers used with the old engine are retained in 
place, with more or less cleaning and patching, as the case may 
require. Now, it is evident to any practical mind that boilers 
constructed for a twenty-horse power engine are ill adapted to 
an engine of forty-horse power, more especially if those boilers 
have been used for a number of years. In order to supply 
sufficient steam for the new engine, with a cylinder of increased 
capacity, the boiler must be worked beyond its safe working- 
pressure, consequently excessive heating and pressure greatly 
weaken it and endanger the lives of those employed in the vicinity. 
The danger and impracticability of using boilers with too 
limited steam-room may be explained thus : Suppose the entire 
steam -room in a boiler to be six cubic feet, and the contents of 
the cylinder which it supplies to be two cubic feet ; then at each 
stroke of the piston one-third of all the steam in the boilers is 
discharged, and consequently, one- third of the pressure on the 
surface of the water before that stroke is relieved ; hence, it will 
be seen that excessive fires must be kept up in order to generate 
steam of sufficiently high temperature and pressure to supply the 
demand. The result is that the boilers are strained and burned. 
Such economy in boiler power is exceedingly expensive in fuel, 
to say nothing of the danger. Excessive firing distorts the fire- 
sheets, causing leakage, undue and unequal expansion and con- 
traction, fractures, and the consequent evils arising from external 
corrosion. Excessive pressure arises generally from a desire on 
the 13 art of the steam -user to make a boiler do double the work for 



HANDBOOK ON ENGINEERING. 453 

wliicli it was originally intended. A boiler that i.s constructed to 
work safely at from fifty to sixty pounds was never intended to 
run at eighty and ninety pounds ; more especially if it had been 
in use for several j'ears. Boilers deteriorated by age should have 
their pressure decreased, rather than increased. 

One of the first things that should be done in manufacturing 
establishments would be to provide sufficient boiler power and, in 
order to do this, the work to be done ought to be accurately cal- 
culated and the engine and boilers adapted to the results of this 
calculation. Steam users themselves are frequently to blame for 
the annoyances and dangers arising from unsafe boilers and those 
of insufficient capacity. From motives of false economy they are 
too easily swayed in favor of the cheaper article, simply because 
it is cheap, when they should consider they are purchasing an 
article which, of almost all others, should be made in the most 
thorough manner and of the best material. In view of the fearful 
explosions that occur from time to time, every steam user should 
secure for his use the best and safest. The object of a few 
dollars as between the work of a good, responsible maker and 
that of an irresponsible one, should not for one moment be 
entertained. 

It is very bad policy for steam-users to advertise for estimates 
for steam-boilers, or to inform all the boiler-makers in the town 
or city that a boiler or boilers to supply steam for an engine of a 
certain size is needed, because in this way steam-users frequently 
find themselves in the hands of needy persons, who, in their 
anxiety to get an order, will sometimes ask less for a boiler than 
they can actually make it for ; consequently, they have to cheat 
in the material, in the workmanship, in the heating-surface and in 
the fittings. As a result, the boiler is not only a continual source 
of annoyance, but, in many instances, an actual source of danger. 
The most prudent course, and in fact the only one that may be 
expected to give satisfaction, is to contract with some responsible 



454 HANDBOOK ON ENGINEERING. 

inauufacturer that lias aii established reputation for honesty, 
capability and fair dealing, and who will not allow himself to be 
brought in competition with irresponsible parties for the purpose 
of selling a boiler. There are thousands of boilers designed, con- 
structed and set up in such a manner as to render it utterly 
impossible to examine, clean or repair them. Generally, in such 
cases, in consequence of imperfect circulation, the water is 
expelled from the surface of the iron at the points where the 
extreme heat from the furnace impinges, and, as a result, the 
plates become overheated and bulge outward, which aggravates 
the evil, as the hollow formed by the bulge becomes a receptacle 
for scale and sediment. By continued overheating, the parts 
become crystallized and either crack or blister ; this, if not 
attended to and remedied, will eventually end in the destruction 
of the boiler. Many boilers, to all appearance well made and of 
good material, give considerable trouble by leakage and fracture, 
owing to the severe strains of unequal expansion and contraction 
induced by the rigid construction, the result of a want of skill in 
the original design. 

DESIGN OF STEAM=BOILERS. 

It has become a general assertion on the part of writers on the 
steam-boiler that the most important object to be attained in its 
design and arrangement is thorough combustion of the fuel. 
This is only partially true as there are other conditions equally 
important, among which are strength, durability, safety, economy 
and adaptability to the particular circumstances under which it is 
to be used. However complete the combustion may be, unless 
its products can be easily and rapidly transferred to the water, 
and unless the means of escape of the steam from the surfaces on 
which it is generated is easy and direct, the boiler will fail to 
produce satisfactory results, either in point of durability or 
economy of fuel. 



HANDBOOK ON ENGINEERING. 455 

Strength means the power to sustain the internal pressure to 
which the boiler may be subjected in ordinary use, and under 
careful and intelligent management. To secure durability, the 
material must be capable of resisting the chemical action of the 
minerals contained in the water, and the boiler ought to be 
designed so as to procure the least strain under the highest state 
of expansion to which it may be subjected — be so constructed 
that all the parts will be subjected to an equal expansion, con- 
traction, push, pull and strain, and be intelligently and thoroughly 
cared for after being put in use. These objects, however, can 
only be obtained by the aid of a knowledge of the principles of 
mechanics, the strength and resistance of materials, the laws of 
expansion and contraction, the action of heat on bodies, etc. 
The economy of a steam boiler is influenced by the following con- 
ditions : cost and quantity of the material, design, character of the 
workmanship employed in its construction, space occupied, capa- 
bility of the material to resist the chemical action of the ingredi- 
ents contained in the water, the facilities it affords for the 
transmission of the heat from the furnace to the water, etc. The 
safety of any structure depends on the designer's knowledge of 
the principles of mechanics, the resistance of materials and the 
action of bodies as influenced by the elements to which they are 
exposed ; and in the case of steam boilers, the safety depends on 
the judgment of the designer, the quality of the material, the 
character of the workmanship and the skill employed in the man- 
agement. Safety is said to be incompatible with economy, but 
this is undoubtedly a mistake, as an intelligent economy includes 
permanence and seeks durability. Adaptability to the peculiar 
purposes for which they are to be used is one of the first objects 
to be sought for in the design and construction of any class of 
machines, vessels or instruments, and it is undoubtedly this that 
gave rise to the great variety of designs, forms and modifications 
of steam boilers in use at the present day, which are, with very 



45 n HANDBOOK ON ENGINEERING. 

few exceptions, the result of thought, study, investigation and 
experiment. 

FORMS OF STEAH BOILERS. 

According to the well-known law of hydrostatics, the pressure 
of steam in a close cylindrical vessel is exerted equally in all 
directions. In acting against the circumference of a cylinder, 
the i^ressure must, therefore, be regarded as radiating from the 
axis, and exerting a uniform tensional strain throughout the 
inclosing material. 

Familiarity with steam machinery, more especially with boil- 
ers, is apt to beget a confidence in the ignorant which is not 
founded on a knowledge of the dangers by which they are contin- 
ually surrounded ; while contact with steam, and a thoroughly 
elementary knowledge of its constituents, theory and action, only 
incline the intelligent engineer and fireman to be more cautious 
and energetic in the discharge of their duties. Many regard 
steam as an incomprehensible mystery ; and although they may 
employ it as a power to accomplish work, know little of its 
character or capabilities. Steam may be managed by common 
sense rules as well as any other power ; but if the laws which 
regulate its use are violated, it reports itself, and often in louder 
tones than is pleasant. If steam-boilers in general were better 
cared for than they are, their working age might be greatly in- 
creased. Deposits of incrustation, small leaks and slight cor- 
rosion, are too often neglected as matters of little consequence, 
but they are the forerunners of expensive repairs, delay and 
disaster. 

SETTING STEAM-BOILERS. 

While engineers differ very much in opinion respecting the best 
manner of setting boilers, they all readily allow that the results 
obtained, as regards economy of fuel and the generation of steam, 



HANDBOOK ON ENGINEERING. 457 

depend in a great measure on the arrangement of the setting. 
Particularly is this the case with horizontal tubular boilers, and 
there have been numerous plans introduced to obtain a maximum 
of steam with a minimum of fuel. Some of the most practical 
designs and best laid plans are frequently rendered useless for 
want of knowledge on the part of those whose duty it is to exe- 
cute or carry them out. This has perhaps been more frequently 
the case as regards the setting of steam boilers than any other 
class of machines, as it is customary for owners of steam boilers 
to depend too much on the knowledge of masons and bricklayers ; 
consequently, a great many blunders have been made which 
necessitated changes in the size of gratebars, alteration of brick- 
work, alteration of flues, chimney, etc., with a list of other annoy- 
ances, such as insufficiency of steam, poor draught, or something 
else. In setting or putting in boilers, all the surface possible should 
be exposed to the action of the heat of the fire, not only that the 
heat may be thus completely absorbed, but that a more equal ex- 
pansion and contraction of the structure may be obtained. Long 
boilers are often hung by means of loops riveted to the top of 
them and connected to crossbeams and arches resting on masonry 
above them, by means of hangers. This is a very mischievous 
arrangement, unless turn-buckles, or some other contrivance, are 
used to maintain a regular strain on all the hangers, as long boil- 
ers exposed to excessive heat are apt to lengthen on the lower 
side and relieve the end hangers of any weight ; consequently, 
the whole strain is transmitted to the central hanger, which has a 
tendency to draw the boiler out of shape — in many instances 
inducing excessive leakage, rupture, and, eventually, explosion. 

DEFECTS IN THE CONSTRUCTION OF STEAM BOILERS. 

The following cuts illustrate some of the mechanical defects 
that impair the strength and limit the safety and durability of 



458 



HANDBOOK ON ENGINEERIN(J 



steam boilers. All punched holes are conical, and unless the 
sheets are reversed after being punched, so as to bring the 
small sides of the holes together, it will be impossible to fill them 
with the rivets. Fig. 1 shows the position of the rivet in the 
hole without the sheets being reversed ; and it will be observed 
that, as very little of the rivet bears against the material, the ex- 
pansion and contraction of the boiler have a tendency to work it 
loose. It is apparent that such a seam would not possess over 
one-third the streno^th that it would if the holes in the sheets 



Fig. 1. 





Fio:. 2. 



Fig. 






Fi.o^. 6. 



were reversed and thoroughly filled with the rivet, as shown in 
Fig. 2. Fig. 3 represents what is known in boiler-making as a 
blind-hole, which means that the holes do not come opposite 
each other when the seams are placed together for the purpose of 
riveting. Fig. 4 shows the position of the rivet in the blind -hole 
after being driven. It will be observed that the heads of the 
rivet, in consequence of its oblique position in the hole, bear only 
on one side, and that even the bearing is very limited, and 
through the expansion and contraction of the boiler, is liable to 



HANDBOOK ON ENGINEERING. 459 

work loose and become leaky. Such a seam would be actually 
weaker than that rej)resented in Fig. 1. Fig. 5 shows the metal 
distressed and puckered on each side of the blind-hole in the 
sheets, which is the result of efforts on the part of the boiler- 
maker, by the use of the drift-pin, to make the holes correspond 
for the purpose of inserting the rivet. Fig. 6 shows the metal 
broken through by the same means. Now, it will be observe^ 
that nearly all the above defects are the result of ignorance and 
carelessness, showing a want of skill in laying out the work, as 
well as a want of proper appliances for that purpose. The evils 
arising from such defects are greatly aggravated by the fact that 
they are all concealed, frequently defying the closest scrutiny, and 
are only revealed by those forces which unceasingly act on boilers 
when in use. Such pernicious mechanical blunders ought to be 
condemned, as they are always the forerunners of destruction 
and death. There can be no reason why boilers should not be 
constructed with the same degree of accuracy, judgment and skill 
as is considered so essential for all other classes of machinery. 

IMPROVEMENTS IN STEAM=BOILERS. 

Until quite recently the steam boiler has undergone very little 
improvement. This arose, perhaps, from the fact that men of 
intelligence and mechanical genius directed their thoughts and 
labors to something more inviting and less laborious than the 
construction of steam boilers. Consequently^, that branch of 
mechanics was left almost entirely to a class of men that had not 
the genius to rise in their profession or improve much in anything 
they attempted. As a result ignorance, stupidity and a kind of 
brute force were the predominant requirements in the construc- 
tion of the steam boiler ; but within the past few years this state 
of things has been changed, as some very important improvements 
have been made, not only in the manufacture of the material of 
which boilers are made, but also in the mode of constructing 



460 HANDBOOK ON ENGINEERING. 

them. Tiie imposing, powerful aud accurate boiler machinery in 
use at the present time is an evidence that the attention of emi- 
nent mechanics and manufacturers is directed to the steam boiler, 
and that in the future its improvement will keep pace with that of 
the steam engine. 

Boiler-plate is now rolled of sufficient dimensions to form the 
rings for boilers of any diameter with only one seam, obviating 
the necessity of bringing riveted seams in contact with the fire, 
as was usually the case in former times. In the manner of laying 
off the holes for the rivets, accurate steel gauges have taken the 
place of the old-fashioned wooden templet, thereby removing the 
evils induced by blind-holes, and obviating the necessity of using 
the drift-pin. So, also, in the method of bending the sheets to 
form the requisite circle — with a better class of machinery, the 
work is now more accurately performed. The old process of chip- 
ping is, in nearly all the large boiler-shops, superseded by planing 
the bevels on the edge of the sheet, preparatory to calking. Recent 
improvements in " calking " have resulted in perfect immunity from 
the injuries formerly inflicted on boilers in that process. 
In most establishments of any repute in this country, riveting is 
done by machinery, which is (as is well known to all intelligent 
mechanics) very much superior to hand-riveting. It is only 
small shops that enter into rivalry to secure orders and build 
cheap boilers, using poor material and an inferior quality of 
mechanical skill, that use the same old crude appliances — in 
many cases the merest makeshifts — that were in use a quarter of 
a century ago, and constructed without regard to any of the rules 
of design that are considered so essential in appliances for the 
construction of all other classes of machinery. Every engineer 
should inform himself on the subject of the safe working pressure 
of boilers, and when he finds the limit of safety has been reached, 
he should promptly inform his employer and use his influence to 
have the boiler worked within the bounds of safety. 



HANDBOOK ON ENGINEERING. 461 

To find the heating surface of a water tube boiler : — 

Rule. — Add the combined outside area of the tubes in square 
feet to one-half the area of the shell of the steam drum in square 
feet and the sum will give the total heating surface. 

Example !♦ — What is the heating surface of a water tube 
boiler having fifty tubes, each three inches outside diameter and 
fifteen feet long, and the steam drum thirty-two inches in 
diameter and fifteen feet long ? 

Operation* — 3 X 3.1416 equals 9.4248 inches, the circumfer- 
ence of one tube. 15 X 12 equals 180 inches the length of one 

9.4248 X 180 
tube. t-Ta. equals 11.781 square feet in one tube, and 

11.781 X 50 equals 589.05 square feet of heating surface in fifty 

32 X 3.1416 
tubes. Then, r-x equals 8.3776 linear feet the circum- 
ference of the steam drum and 8.3776 X 15 equals 125.664 square 

125.664 
feet of heating surface in steam drum, and ^ equals 62.832 

square feet, half the heating surf ace of steam drum. 

Then, 589.05 plus 62.832 equals 651.882 square feet, the total 
heating surface. Answer. 



STRENGTH OF RIVETED SEAHS. 

The strength of a riveted seam depends very much upon the 
arrangement and proportion of the rivets ; but with the best 
design and construction, the seams are always weaker than the 
solid plate, as it is always necessary to cut away a part of 
the plate for the rivet holes, which weakens the holes in three 
ways : 1st, by lessening the amount of material to resist the 
strains; 2d, by weakening that left between the holes; 3d, by 
disturbing the uniformity of tlie distribution of the strains. 



462 HANDBOOK ON ENGINEERING. 

COMPARATIVE STRENGTH OF SINGLE AND DOUBLE 
RIVETED SEAMS. 

On comparing the strength of plates with riveted joints, it will 
be necessary to examine the sectional areas taken in a line through 
the rivet-holes, with the section of the plates themselves. It is 
obvious that in perforating a line of holes along the edge of a 
plate, we must reduce its strength. It is also clear that the plate 
so perforated will be to the plate itself nearly as the areas of their 
respective sections, with a small deduction for the irregularities 
of the pressure of the rivets upon the plate ; or, in other words, 
the joint will be reduced in strength somewhat more than in the 
ratio of its section through that line to the solid section of the 
plate. It is also evident that the rivets cannot add to the strength 
of the plates, their object being to keep the two surfaces of the 
lap in contact. When this great deterioration of strength at the 
joint is taken into account, it cannot but be of the greatest 
importance that in structures subject to such violent strains as 
boilers, the strongest method of riveting should be adopted. To 
ascertain this, a long series of experiments was undertaken by 
Mr. Fairbairn. There are two kinds of lap-joints, single and 
double-riveted. In the early days of steam-boiler construction, 
the former were almost universally employed ; but the greater 
strength of the latter has since led to their general adoption for 
all boilers intended to sustain a high steam pressure. A riveted 
joint generally gives way either by shearing off the rivets in the 
middle of their length, or by tearing through one of the plates in 
the line of the rivets. 

In a perfect joint, the rivets should be on the point of shearing 
just as the plates were about to tear; but, in practice, the rivets 
are usually made slightly too strong. Hence, it is an established 
rule to employ a certain number of rivets per linear foot, which 
for ordinary diameters and average thickness of plate, are about 



HANDBOOK ON ENGINEERING. 468 

six per foot or two inches from center to center ; for larger 
diameters and heavier iron, the distance between the centers 
is generally increased to, say 2^ or 2i inches ; but in such 
cases it is also necessary to increase the diameter of the rivet, 
for while |, or even ^ inch rivets will answer for small diameters 
and light plate, with large diameters and heavy plate, experi- 
ence has shown it to be necessary to use J to J rivets. If 
these are placed in a single row, the rivet holes so nearly 
approach each other that the strength of the plates is much 
reduced ; but if they are arranged in two lines, a greater number 
may be used, more space left between the holes and greater 
strength aud stiffness imparted to the plates at the joint. 
Taking the value of the plate before being punched, at 100, by 
punching the plate it loses 44 per cent of its strength ; and, as a 
result, single-riveted seams are equal to 56 per cent, and double- 
riveted seams to 70 per cent of the original strength of the plate. 
It has been shown by very extensive experiments at the Brooklyn 
Navy Yard, and also at the Stevens Institute of Technology, 
Hoboken, N. J., that double-riveted seams are from 16 to 20 per 
cent stronger than single-riveted seams — the material and work- 
manship being the same in both cases : 

Taking the strength of the plate at 100 

The strength of the double-riveted joint would then be . . 70 
The strength of the single-riveted would be 56 

To find the thickness of plates for the shell of a cylindrical 
boiler for a required safe working pressure in pounds per square 
inch : — 

Rule* — Multiply the required pressure per square inch by the 
radius of the shell in inches, and by the constant number 6 for 
single riveted side seams, and divide the last product by the 
tensile strength of the plates. For double riveted side seams use 
the constant number 5 instead of 6. 

Example i* — What should be the thickness of plates for a boiler 
§0 inches iii diameter , with single riveted side seams, for a work-^ 



464 



HANDBOOK ON ENGINEERING. 



iDg pressure of 125 pounds per square inch, the tensile strength 

of the plates being 60,000 pounds per square inch? 

125 X 30 X 6 
Operation^ — n^ qqq equals .375 or 3/8 in. Answer. 

Example 2* — What should be the thickness of plates for a 

boiler 60 inches diameter, with double riveted^side seams, for a 

working pressure of 150 pounds per square inch, the tensile 

strength of plates being 60,000 pounds per square inch. 

150 X 30 X5 
Operation* — ^q qqq equals .375 or 3/8 in. Answer. 

The following: formulas, equivalent to those of the British 
Board of Trade, are given for the determination of the pitch, 
distance between rows of rivets, diagonal pitch, maximum pitch, 
and distance from centers of rivets to edge of lap of single and 
double riveted lap joints, for both iron and steel boilers': — 

Let 2^ = greatest pitch of rivets, in inches ; 
?i = number of rivets, in one pitch ; 
p^ = diagonal pitch, in inches ; 
d =z diameter of rivets, in inches ; 
T r=r thickness of plate, in inches ; 
V= distance between rows of rivets, in inches ; 
E = distance from edge of plate to center of rivet, in inches. 

TO DETERMINE '^HE PITCH. 

Iron plates and iron rivets — 

P = J, ■ + d. 

Example: First, for single-riveted joint — 

Given, thickness of plate (T)=^- inch, diameter of rivet 

(d) = |- inch. In this case, n = 1. Required, the pitch. 

Substituting in formula, and performing operation indicated. 

(iy X .7854 X 1 
Pitch = '^8^'-^^- ^-^ -f 7 ::^ 2.077 inches. 



HANDBOOK ON ENGINEERING. 465 

For double-riveted joint — 

Given, t=^ inch, and d = {^ inch. In this case, 7i = 2, 
Then — 

(xs.\2 x/ 7854 V 2 
Pitch = Ue; X./504 x^ +13^ 2.886 inches. 

For steel plates and steel rivets : — 

23 X d^ X ^^ , ^ 

^^^- 28xr +^' 

Example, for single -riveted joint : Given, thickness of plate ^ i 
inch, diameter of rivet = i| inch. In this case, n = l. 
Then — 

Pitch =. ^^X(^t);X.7854xl ^,._,,,^ ,^^,^^_ 

Example, for double-riveted joint : Given, thickness of plate = i 
inch, diameter of rivet = J inch. ?i= 2. Then — 

Pitch = ^AX«4><:I5^1><-V4 = 2.8o iaches. 

28 Xi 

FOR DISTANCE FROM CENTER OF RIVET TO EDGE OF LAP. 

oXd 



E = ^ 



Example : Given, diameter of rivet (c?) = J inch ; required, the 
distance from center of rivet to edge of plate. 

E = ^-^= 1.312 inches, 

for single or double riveted lap joint. 

FOR DISTANCE BETWEEN ROWS OF RIVETS. 

The distance between lines of centers of rows of rivets for 

double, chain-riveted joints (F) should not be less than twice the 

diameter of rivet, but it is more desirable that V should not be 

, 4rf 4 1 
less than 



466 HANDBOOK ON ENGINEERING. 

Example under latter formula: Given, diameter of rivet = J 
inch, then — 

V= ^^ X |) + ^ ^2.25 inches. 
For ordinary, double, zigzag -riveted joints, 



^,^ V(lll>+4c^) ( P^^d) 



10 

Example : Given, pitch = 2.85 inches, and diameter of rivet = J 
inch, then — 



DIAGONAL PITCH. I 

For double, zigzag-riveted lap joint. Iron and steel. 

6p + 4rf 

Example : Given, pitch = 2.85 inches, and d = ^ inch, then — 
2M = ~—^ m =2.06 mches. 

MAXIMUM PITCHES FOK RIVETED LAP JOINTS. 

For single-riveted lap joints, maximum pitch=(1.31x ^)~f If' 
For double-riveted lap joints^ maximum pitch ^=(2.62Xj^) + 1|- 
Example: Given a thickness of plate = i inch, required, the 

maximum pitch allowable. 

For single-riveted lap joint, maximum pitch = (1.31 X |) + 

If = 2.28 inches. 

For double-riveted lap joint, maximum pitch = (2.62 X i) + 

1| = 2.935 inches. 

The following tables, taken from the handbook of Thomas W. 
Traill, entitled "Boilers, Marine and Land, their Construction 



HANDBOOK ON ENGINEERING. 



467 



and Strength," may be taken for use in single and double riveted 
joints, as approximating the formulas of the British Board of 
Trade for such joints : — 

IRON PLATES AND IRON RIVETS. 

DOUBLE-RIVETED LAP JOINTS. 











Distance between rows 








Center of 


of rivets. 


Thickness 


Diameter 


Pitch of 


rivets to 




of plates. 


of rivets. 


rivets. 


edge of 












plates. 


Zigzag 
riveting. 


Chain 
riveting. 


T 


d 


P 


E 


V 


V 


t 


% 


2.272 


.937 


1.145 


1.750 


ik 


2.386 


.984 


1.202 


1.812 


■ 


1^ 


2.500 


1.031 


1.260 


1.875 




23 
3 2 


2.613 


1.078 


1.317 


1.937 


¥ 




2.727 


1.125 


1.374 


2.000 


i' 


II 


2.826 


1.171 


1.426 


2.062 


il 


2.886 


• 1.218 


1.465 


2.125 


ii 


32 


2.948 


1.265 


1.504 


2.187 


f 


I - 


3.013 


1.312 


1.544 


2.250 


d 


3.079 


1.359 


1.585 


2.312 




-f 


3.146 


1.406 


1.626 


2.375 


li 


'■zh 


3.215 


1.453 


1.667 


2.437 


t? 


1 


3.284 


1.500 


1.709 


2.500 


32 


I3V 


3.355 


1.546 


1.751 


2.562 


L 


l-lV 


3.426 


1.593 


1.794 


2.625 




1-3^- 


3.498 


1.640 


1.836 


2.687 


U 


3.571 


1.687 


1.879 


2.750 


32 


lA 


3.645 


1.734 


1.923 


2.812 


\ 


itV 


3.718 


1.781 


1.966 


2.875 


P 


h^ 


3.793 


1.828 


2.009 


2.937 


ii 


u 


3.867 


1.875 


2.053 


3.000 


i^ 


lA 


3.942 


1.921 


2.096 


3.062 


1 


1-A- 


4.018 


1.968 


2.140 


3.125 



468 



HANDBOOK ON ENGINEERING. 




ZIOZAO EIVETINO. 




^f^^_ p ^.i_t 




6 S- 

) O t 


'^ 

E 

V 

E 

jt 


__—— 





CHAIN RIVETING. 





HANDBOOK ON ENGINEERING. 469 

IRON PLATES AND IRON RIVETS. 



SINGLE-RIVETED LAP JOINTS, 




Thickness of 


Diameter of 


Pitch of 


Center of rivets to 


plates. 


rivets. 


rivets. 


edge of plates. 


T 


d 


i' 


E 


i 


1 


1.524 


.937 




u 


1.600 


.984 


■ ^ 




1.676 


1.031 


;^ 


H 


1.753 


1.078 




1.829 


1.125 


32 


32 


1.905 


1.171 


-L. 


1.981 


1.218 


32 


^- 


2.036 


1.265 


h 




2.077 


1.312 


ii 


?^ 


2.120 


1.359 


4 


16 


2.164 


1.406 


n 


3I 


2.210 


1.453 






2.256 


1.500 


fi 


I3V 


2.304 


1.546 


hV 


2.352 


1.593 


2 
3 


1-3% 


2.400 


1.640 


L 


\ 


2.450 


1.687 






2.500 


1.734 


6 


1-1% 


2.550 


1.781 


32" 


1^ 


2.601 


1.828 


I 


1^ 


" 2.652 


1.875 


II 


1^ 


2.703 


1.921 


ii4 


2.755 


1.968 



470 HANDBOOK ON ENGINEERING. 

STEEL PLATE AND STEEL RiVETS. 



SINGLE-RIVETED LAP JOINTS. 




Thickness of 


Diameter of 


Pitch of 


Center of rivets 

to edge of 

plates. 


plates. 


rivets. 


rivets. 


T 


d 


P 


E 


h 


II 


1.562 


1.031 


-3^2 


1.633 


1.078 


A 


1 


1.704 


1.125 


3H 


11 


1.775 


1.171 


1 


1.846 


1.218 


if 


I2 


1.917 


1.265 


-h 


^ 


1.988 


1.312 


H 


3I 


2.036 


1.359 




J-4 


2.071 


1.406 


il- 


32 


2.108 


1.453 


ii 




2.146 


1.500 




1-3^2- 


2.186 


1.546 


1 


1-A 


2.227 


1.593 


li 


If 


2.269 


1.640 


iH 


2.312 


1.687 


II 




2.356 


1.734 




li 


2.400 


1.781 


32 


2.445 


1.828 


fi 


1^ 


2.500 


1.875 


f 


lA 


2.562 


1.921 




2.623 


1.968 


11 


la^ 


2.687 


2.015 


il 


If' 


2.760 


2.062 



HANDBOOK ON ENGINEERING. 



471 



STEEL PLATE AND STEEL RIVETS. 

DOUBLE-RIVETED LAP JOINTS. 











Distance between rows 








Center of 


of rivets. 


Thickness 


Diameter 
of rivets. 


Pitch of 
rivets. 


rivets to 
edge of 






of plates. 












plates. 


Zigzag 
riveting. 


Chain 
riveting. 


T 


. d 


P 


E . 


V 


V 


-h 


\k 


2.291 


1.031 


1.187 


1.875 


H 


II 


2.395 


1.078 


1.240 


1.937 




1 


2.500 


1.125 


1.295 


2.000 


W 


32 


2.604 


1.171 


1.349 


2.062 


-h 


fl 


2.708 


1.218 


1.403 


2.125 


15. 
3 2 


32 


2.803 


1265 


1.453 


2.187 




1 


2 850 


1.312 


1.487 


2.260 


h 


32 


2.900 


1.359 


1.522 


2.312 




if 


2.953 


1.406 


1.558 


2.375 


32 


32 


8.008 


1.453 


1.595 


2.437 


1 


1 


3.064 


1.500 


1.631 


2.500 




I3V 


3.122 


1.546 


1.669 . 


2.562 


i! 


l-lV 


3.181 


1.593 


1.707 


2.625 


3 2 


I-3V 


3.241 


1.640 


1.745 


2.687 


1 


u 


3.302 


1.684 


1.784 


2.750 


It 


1^2- 


3.364 


1.734 


1.823 


2.812 


1-1% 


3.427 


1.781 


1.863 


2.375 


|i 


^-h 


3 490 


1.828 


1.902 


2.937 


l" 


u 


3.554 


1.875 


1.942 


3.000 


^i 


1-3^ 


3.618 


1.921 


1.981 


3.062 


le 


1?% 


3.683 


1.968 


2.021 


3.125 


it 

3 2 


IH 


3.748 


2.015 


2.061 


3.187 


1 


If 


3.814 


2.062 


2.102 


3.250 



472 



HANDBOOK ON ENGINEEKINa. 



ZIGZAG RIVETII^G. 





CHAIN RIVETING. 





HANDBOOK ON ENGINERllING. 473 

STRENGTH OF STAYED AND FLAT BOILER SURFACES. 

The sheets that form the sides of fire-boxes are necessarily 
exposed to a vast pressure, therefore, some expedient has to be 
devised to prevent the metal at these parts from bulging out. 
Stay-bolts are generally placed at a distance of 4i inches from 
center to center, all over the surface of fire-boxes, and thus the 
expansion or bulging of one side is prevented by the stiffness or 
rigidity of the other. Now, in an arrangement of this kind, it 
becomes necessary to pay considerable attention to the tensile 
strength of the stay-bolts employed for the above purpose, since 
the ultimate strength of this part of the boiler is now transferred 
to them, it being impossible that the boiler j^lates should give way 
unless the stay-bolts break in the first instance. Accordingly, 
the experiments that have been made by way of test of the 
strength of stay-bolts, possess the greatest interest for the practi- 
cal engineer. Mr. Fairb urn's experiments are particularly val- 
uable. He constructed two flat boxes, 22 inches square. The 
top and bottom plates of one were formed of i inch copper, and 
of the other, | inch iron. There was a 2iinch water-space to each, 
with if inch iron-stays screwed into the plates and riveted on the 
ends. In the first box the stays were placed five inches from 
center to center, and the two boxes tested by hydraulic pressure. 
In the copper box, the sides commenced to bulge at 450 lbs. 
pressure to the sq. in. ; and at 815 lbs. pressure to the sq. in. 
the box burst, by drawing the head of one of the stays through 
the copper plate. In the second box, the stays were placed at 
4-inch centers; the bulging commenced at 515 lbs. pressure to 
the sq. in. The pressure was continually augmented up to 1,600 
lbs. The bulging between the rivets at that pressure was one- 
third of an inch ; but still no part of the iron gave way. At 
1,625 lbs. pressure the box burst, and in precisely the same way 
as in the first experiment — one of the stays drawing through the 



474 HANDBOOK ON ENGINEERING. 

iron plate and stripping the thread in plate. These experiments 
prove a number of facts of great value and importance to the 
engineer. In the first place, they show that with regard to iron 
stay-bolts, their tensile strength is at least equal to the grip of 
the plate. 

The ^fip of the copper bolt is evidently less. As each stay, 
in the first case, bore the pressure on an area of 5 x 5 = 25 square 
inches, and in the second on an area 4x4 1= 16 sq. inches, the 
total strains borne by each stay were, for the first, 815x25 = 
20,375 pounds on each stay; and for the second, 1,625 x 16 = 
26,000 lbs. on each stay. These strains were less, however, than 
the tensile strength of the stays, which would be about 28,000 
lbs. The properly stayed surfaces are the strongest part of boil- 
ers, when kept in good repair. 

BOILER-STAYS. 

Advantage is usually taken of the self-supporting property of 
the cylinder and sphere, which enables them, in most cases, to be 
made sufficiently strong without the aid of stays or other support. 
But the absence of this self-sustaining property in flat surfaces 
necessitates their being strengthened by stays or other means. 
Even where a flat or slightly dished surface possesses sufficient 
strength to resist the actual pressure to which it is subjected, it is 
yet necessary to apply stays to provide against undue deflection 
or distortion, which is liable to take place to an inconvenient de- 
gree, or to result in grooving, long before the strength of plates 
or their attachments is seriously taxed. Boiler stays, in any 
case, are but substitutes for real strength of construction. They 
would be of no service applied to a sphere subject to internal 
pressure ; and the power of resistance would be exactly that of 
the metal to sustain the strain exerted upon all its parts alike. 
The manner in which stays are frequently employed renders them 
a source of weakness rather than an element of strength. When 



HANDBOOK ON ENGINEERING. 475 

the strain is direct the power of resistance of the stay is equal to 
the weight it would sustain without tearing it asunder ; but when 
the position of the stay is oblique to the point of resistance, any 
calculation of their theoretic strength or value is attended with 
certain difficulties. All boilers should be sufficiently stayed to 
insure safety, and the material of which they are made, their 
shape, strength, number, location and mode of attachment to the 
boiler, should all be duly and intelligently considered. Boiler 
stays should never be subjected to a strain of more than one- 
eighth of their breaking strength. The strength of boiler stays 
may be calculated by multiplying the area in inches between the 
stays by the pressure in pounds per square inch. 

Rule for finding the strain allowed on a diagonal boiler head 
brace or stay ; also rule for finding the number of stays required 
for a certain size crown sheet. 

A — Iron stays should not be subjected to a greater stress than 
from 7,000 to 9,000 pounds per square inch of section, and if 
they are located obliquely, the diameter will need to be increased 
an amount that depends on the angle of the stay to the shell. 
Find the area in square inches to be supported by the stay, and 
multiply it by the pressure per square inch, multiply the product 
by the length of the diagonal stay, and divide the result by the 
perpendicular length from the flat surface to the end of the stay. 
The quotient will be the stress on the stay, and to obtain the 
diameter, divide the stress by the allowable stress per square inch 

of section, and the quotient 
by .7854. The square root of 
the last quotient will be the 
diameter of the stay. 

Thus^ in the accompanying 
diagram, we wish to find the 
diameter of the diagonal stay 
^1, which supports an area 6" x 8" or 48 square inches. The 




476 HANDBOOK ON ENGINEERING. 

length of the stay is 25", and the jjerpendicular distance be- 
tween the stayed surface and the end of the stay is 24.148". 
The boiler pressure is 100 pounds gauge, so that the 
pressure on the surface supported will be 48 x 100 or 4,800 
pounds. We multiply 4,800 by 25 and divide the product by 
24.148", which gives 4,970, nearly. The quotient of 4,970, 
divided by 7,000 equals .71; .71, divided by .7854 equals 
.9039, and the square root of this is .95 or .95", the diameter of 
a stay that will support 48 square inches in the position shown. 
A convenient formula for finding the diameter of oblique stays 

is, 

D equals 1.13^ 

D equals diameter of the stay. 

A " area in square inches to be supported. 

P " pressure per square inch. 

L " safe load per square inch of stay section. 

B " angle between the shell and the stay. 

Using the preceding problem as an example and referring to 
the same diagram, we have angle B equal to 15°, and all the other 
dimensions as previously given. Therefore, 



j^ , , ,o l48 X 100 

i> equals 1.13^ — ^ 



7000 X .96593 

The diameter of the stay, when the above is simplified, is 
.9526", or practically 1". A rule for finding the pitch of stays 
for any flat surface is given below. 

t* A safe formula for the strength of stayed flat surfaces is 
that given by Unwin's machine design. When the spacing of 
the stays is desired, assuming that it is the same in each direc- 
tion, we have. 



a equals 3 t 



\2p 



HANDBOOK ON ENGINEERING. 477 

where a equals spacing of stays or rivets in inches,/ equals safe 
working strength of the i3late, t equals thickness of plate, and p 
equals boiler pressure. Expressed as a rule, this reads: Divide 
the safe strength of the plate by twice the pressure ; extract the 
square root of the quotient and multiply the final result by three 
times the thickness of the plate. The result will be the spacing 
of the stays in inches. For example, boiler pressure 100 pounds, 
plate 1/2 inch thick, safe strength of plate, 10,000 pounds per 
square inch ; 2p equals 2 x 100 equals 200 ; //2p equals 10000/200 
equals 50; V 50 equals 7.07; 3^ equals 3/2 equals 1-1/2 equals 
1.5; 7.07x1.5 equals 10.6 for the spacing. In making such a 
calculation care must be exercised not to assume too high values 
for the strength of the plate. It is not safe to count on more 
than 60,000 pounds for the strength of steel plates and 40,000 
for iron. The working strength must be taken not higher than 1/6 
of this, or 10,000 for steel and 6,666 for iron, and lower values 
still would be better, say 9,000 for steel and 6,000 for iron. 

2* The safe pressure for a boiler to carry, so far as the 
flat, stayed surfaces are concerned, may be found from the 
above formula by transposing it a little, as follows: — 

9 t\f 
p equals ~Y^ 

Now, applying this to the above example, we have p equals 

9x.52xl0000 ,., ^ 9 x. 25x10000 , ,., , 

-^^ — TTTTi^ — which equals —-: — , ^^ ^^ — and which after re- 
2x 110.20 ^ 2x110.25 

22500 
duction equals - equals 102, or substantially the pressure 

^^o.oo 

assumed in the first example. 

RIVETED AND LAP WELDED FLUES. 

The following table shall include all riveted and lap-welded 
flues exceeding 6 inches in diameter and not exceeding 40 inches 
in diameter not otherwise provided by law, as required by U. S. Gov. 



478 



HANDBOOK ON ENGINEERING. 



§*^'^SS'^t^k!g^S2gggS3k*^^K^^§S 




3 

3* 


Thickness of material 
required. 


5"! 
o 


'oooacioooooooaooooooo 
s-p'p-D-p'p-ptrcrp'p-B-cr vpr tr p- cr cr p- D- 










Pounds 
pres 
sure. 
189 
194 
199 
204 


Over 6 and 
not over 7 
, inclies. 


C 
B 

o 

tit 

o 


p-oo 

Is 

h 

5". 

p-t- 


^1 

O 

1! 

B 


i 








iiSi^ 




32i 


Over 7 and 
not over 8 
Inches. 


II 






lilSIS: 




III 


Over 8 and 
not over 9 
inches. 


o 




;:;::;::::: IS^I^SS: 






Over 9 and 
not over 10 
inches. 


N i M M M n gigsssM 




2?| 


Over 10 and 
not over 11 
inches. 


Ik 
lb 

Ik 

a . 
P^ 

B . 

ik 

a 
g-S 

Is 

5". 
g-g 

k 


a 

C3 

o 
S 

p 

O 




> 


::::::•;: sli^SSSi; : 




ill 


Over 11 and 
not over 12 
inches. 




::::::: IS^SSSIIs 






ill 


Over 12 and 
not over 13 
inches. 


a 




*::::: ISiisSIIIS: 






ill 


Over 13 and 
not over 14 
inches. 


a 

a 
en? 




: : : : l^ilsSll^is 










Over 14 and 
not over 15 
Inches. 


o 




: : : iSISSIsgl^i 










■ iii 


Over 15 and 
not over 16 
inches. 


o 

a 




136 
141 
146 
152 
156 
161 
167 
172 
177 
182 
187 










•ill 


Over 16 and 
not over 17 
inches. 






; ISSniiSsSSi^ 












III 


Over 17 and 
not over 18 
inches. 


OS 

S" 

a 


: SSSiisSSSiS; 












III 


Over 18 and 
not over 19 
Inches. 




s 


§iigisSSBi: : 












''M 


Over 19 and 
not over 20 
inches. 





HANDBOOK ON ENGINEERING. 



479 



|o 



•saqoai 
fgiaAoqod 

pUB gg I8AO 



•saqoui 
gg J8AO ion 



•eaqout 

Z2 J8AO}OCl 

pat? X8 I9AO 



•eaqoui 
Ig jaAoaou 
puB 08 JaAO 



•saqoui 
Og J8AO ion 
pu« 6Z J^^O 



1J2 



•saqouj 

QZ J8A010U 

puB SZ 18 AO 



ft, '-^ 



•eaqont 
puB ig aaAO 



§ QJ »H 



•saqoui 
puB 92 I9AO 



li?^- 



•soqouT 
paiJ qz J8AO 



•saqoui 
gs J9AO loa 

pUB fg J8AO 

•99qont 

fZ J8AO ?OU 
pUB g?; J8AO 



•saqoui 
g^ jaAo^ou 
puB r.j: I8AO 



•saqoni 

paB X^ J9AO 



•saqoui 
IS J8AO ?od 
put? 02 J!*AO 



eiiOOOr-H-* 



■H r- .-H (M ©q (M 



lO OO O CIS «0 13: * 
r-H r-( C^ (N e>J Cfl W 









^S2;E:S£2=S 



OigjOgC^jgOitNiOOOi-H 






ii0 05<M«50icot:-t— (Tj 



<N (M CO CO CO ■* TT lO .O Iffl to 



»ftOi(Mt-.-^»«Oi(MCOC 



O^lftOSCOt^rHlOOiCOr-- 

sicococo-«#-^mioiooco 



•pajjnbai 
ItJuaiBiu JO seauqoiqx 



Cfloaflflflccflcncflcacflaocqcflca 



oeococofceoco-*T»<^Td 



COJOi— l(MJO-*lOCD 



480 HANDBOOK ON ENGINEERING. 

For any flue requiring more pressure than is given in table, the 
same will be determined by proportion of thickness to any given 
pressure in table to thickness for pressure required, as per exam- 
ple : A flue not over 19 inches diameter and 3 feet long, requires 
a thickness of .39 of an inch for 176 pounds pressure; what 
thickness would be required for 250 lbs. pounds pressure? 

176: .39:: 250: .5539, 

or a thickness of .554 inch. 

Or, if .39 inch thickness gives a pressure of 176 lbs., what will 
.554 inch thickness give? 

.39 : 176 : : .554 : 250 pounds required. 

And all such flues shall be made in sections, according to their 
respective diameters, not to exceed the lengths prescribed in the 
table and such sections shall be properly fitted one into the other 
and substantially riveted, and the thickness of material required 
for any such flue of any given diameter shall in no case be less than 
the least thickness prescribed in the table for any such given 
diameter ; and all such flaes may be allowed the prescribed work- 
ing steam pressure, if in the opinion of the inspectors, it is 
deemed safe to make such allowance. And inspectors are there- 
fore required, from actual measurement of each flue, to make 
such reduction from the prescrib.ed working steam pressure for 
any material deviation in the uniformity of the thickness of the 
material, or for any material deviation in the form of the flue from 
that of a true circle, as in their judgment the safety of navigation 
may require. 

Riveted and lap-welded flues of any thickness of material, 
diameter, and length of sections prescribed in the table, may be 
made in sections of any desired length, exceeding the maximum 
length allowed b}' the table, by reducing the prescribed pressure 



HANDBOOK ON ENGINEERING. 481 

in proportion to the increased length of section, according to the 
following rule : — 

Rule* — Multiply the pressure in the table allowed for any pre- 
scribed thickness of material and diameter of flue by the greatest 
length, in feet, of sections allowable for such flue, and divide the 
l^roduct by the desired length of sections, in feet, from center line 
to center line of rivets, in the circular seams of such sections, and 
the quotient will give the working steam pressure allowable. 

Example. — Taking a flue in the table 24 inches in diameter, 
required to be made in sections not exceeding 2.5 feet in length, 
and having a thickness of material of .44 of an inch, and allowed 
a pressure of 157 lbs., and it is desired to make this flue in sec- 
tions 5 feet in length. 

Then we have 

L_ z= 78.5 lbs. pressure allowable. 

5 

THICKNESS OF MATERIAL REQUIRED FOR TUBES AND FLUES 
NOT OTHERWISE PROVIDED FOR. 

Tubes and flues not exceeding 6 inches in diameter, and made 
of any required length ; and 

Lap- welded flues required to carry a working steam pressure not 
{0 exceed 60 lbs. per square inch, and having a diameter not 
exceding 16 inches, and a length not exceeding 18 feet ; and 

Lap-welded flues required to carry a steam pressure exceeding 
60 lbs. per square inch, and not exceeding 120 lbs. per square 
inch, and having a diameter not exceeding 16 inches and a 
length not exceeding 18 feet, and made in sections not exceeding 
5 feet in length, and fitted properly one into the other, and sub- 
stantially riveted ; and 

AH such flues shall have a thickness of material according 
to their respective diameters, as prescribed in the following 
table : — 

31 



482 



HANDBOOK ON ENGINEERING. 



Outside 
diameter. 


Thickness. 


Outside 
diameter. 


Thickness. 


Outside 
diameter. 


Thickness. 


Inches. 


Inch. 


Inches. 


Inch. 


Inches. 


Inch. 


1 


.072 


H 


.120 


9 


.180 


li 


.072 


Sb. 


.120 


10 


.203 


U 


.083 


31 


.120 


11 


.220 


l| 


.095 


4 


.134 


12 


.229 


2 


.095 


4i 


.134 


13 


.238 


H 


.095 


5 


.148 


14 


.248 


2h 


.109 


6 


.165 


15 


.259 


21 


.109 


7 


.165 


16 


.270 


3 


.109 


8 


.165 







Tubes^ water pipes and steams pipes, made of steel manufac- 
tured by the Bessemer process, may be used in any marine boiler 
when the material from which pipes are made does not contain 
more than .06 per cent of phosphorus and .04 per cent of sulphur, 
to be determined by analysis by the manufacturers, verified by 
them, and copy furnished the user for each order tested ; which 
analysis shall, if deemed expedient by the Supervising Inspector- 
General, be verified by an outside test at the expense of the 
manufacturer of the tubes or pipes. No tube increased in thick- 
ness by welding one tube inside of another, shall be allowed 
for use. 

Seamless copper or brass tubes, not exceeding three-fourths of 
an inch in diameter, may be u'sed in the construction of water 
tube pipe boilers or generators, when liquid fuel is used. There 
may also be used in their construction copper or brass steam 
drums, not exceeding 14 inches in diameter, of a thickness of 
material not less than five-eighths of an inch, and copper or brass 
steam drums 12 inches in diameter and under, having a thickness 
of material not less than one-half inch. . All the tubes and drums 
referred to in this paragraph shall be made from ingots or blanks 
drawn down to size without a seam. Water-tube boilers or gen- 



HANDBOOK ON ENGINEERING. 483 

erators so constructed may be used for marine purposes with 
none other than liquid fuel. 

Lap-welded flues not exceeding 6 inches in diameter may be 
made of any required length without being made in sections. 
And all such lap-welded flues and riveted flues not exceeding 6 
inches in diameter may be allowed a working steam pressure not 
to exceed 225 lbs. per square inch, if deemed safe by the 
inspectors. 

Lap-welded flues exceeding 6 inches in diameter and not 
exceeding 16 inches in diameter, and not exceeding 18 feet in 
length, and required to carry a steam pressure not exceeding 
60 lbs. per square inch, shall not be required to be made in 
sections. 

Lap-welded and riveted flues exceeding 6 inches in diameter 
and not exceeding 16 inches in diameter, and not exceeding 18 
feet in length, and required to carry a steam pressure exceeding 
60 lbs. per square inch, and not exceeding 120 lbs. per square 
inch, may be allowed, if made in sections not exceeding 5 feet in 
length and properly fitted one into the other, and substantially 
riveted. 

On all boilers built after July 1st, 1896, a bronze or brass- 
seated stop-cock or valve shall be attached to the boiler between 
all check valves and all steam and feed pipes and boilers, in order 
to facilitate access to connections. Where such cocks or valves 
exceed 1| inches in diameter, they must be flanged to boiler. 
The stop-valves attached to main steam-pipes may, however, be 
made of cast-iron or other suitable material. The date referred 
to above applies to this paragraph only. 

All copper steam-pipes shall be flanged to a depth of not less 
than four times the thickness of the material in the pipes, and all 
such flanging shall be made to a radius not to exceed the thickness 
of the material in such pipes. And all such pipes shall have a 
thickness of material according to the working steam pressure 



484 HANDBOOK ON ENGINEERING. 

allowed, and such thickness of material shall be determined by 
the following rule : — 

Rule^ — Multiply the working steam pressure in pounds per 
square inch allowed the boiler by the diameter of the pipe in 
inches, then divide the product by the constant whole number 
8000, and add .0625 to the quotient ; the sum will give the thick- 
ness of the material required. 

Example* — Let 175 lbs. = working steam pressure per square 
inch allowed the boiler, 

5 inches = diameter of the pipe, 
8000 =r: a constant. 
Then we have : — 

175x5 

\- .0625 = .1718 -\- thickness of material in decimals of 

oOOO 

an inch. 

The flanges of all copper steam pipes over three inches in 
diameter shall be made of bronze or brass composition, and 
shall have a thickness of material of not less than four times 
the thickness of material in the pipes plus .25 of an inch ; and 
all such flanges shall have a boss of sufl[icient thickness of 
material projecting from the back of the flange a distance of 
not less than three times the thickness of material in the pipe ; 
and all such flanges shall be counter-bored in the face to fit the 
flange of the pipe ; and the joints of all copper steam pipes 
shall be made with a sufficient number of good and substantial 
bolts to make such joints at least equal in strength to all other 
parts of the pipe. 

The terminal and intermediate joints of all wrought iron and 
homogeneous steel feed and steam pipes over 2 inches in diameter 
and not over 5 inches in diameter, other than on pipe or coil 
boilers or steam generators, shall be made of wrought iron, homo- 
geneous steel, or malleable iron flanges, or equivalent material ; 
and all such flanges shall have a depth through the bore of not 



HANDBOOK ON ENGINEERING. 485 

less than that equal to one-half of the diameter of the pipe to which 
any such flange may be attached ; and such bores shall taper 
slightly outwardly toward the face of the flanges ; and the ends 
of such pipes shall be enlarged to fit the bore of the flanges, and 
they shall be substantially beaded into a recess in the face of each 
flange. But where such pipes are made of extra heavy laj^-welded 
steam pipe, the flanges may be attached with screw threads ; and 
all joints in bends may be made with good and substantial 
malleable iron elbows, or equivalent material. 

All feed and steam pipes not over 2 inches in diameter may 
be attached at their terminals and intermediate joints with screw 
threads by flanges, sleeves, elbows, or union couplings ; but 
where the ends of such pipes at their terminal joints are screwed 
into material in the boiler, drum or other connection having a 
thickness of not less than i inch, the flanges of such terminal 
joints may be dispensed with. Where any such pipes are not 
over one inch in diameter and any of the terminal ends are to be 
attached to material in the boiler or connection having a thickness 
of less than i inch, a nipple shall be firmly screwed into the 
boiler or connection against a shoulder, and such pipe shall be 
screwed firmly into such nipple. And should inspectors deem it 
necessary for safety, they may require a jam nut to be screwed 
onto the inner end of any such nipple. 

The word ' ' terminal ' ' shall be interpreted to mean the points 
where steam or feed pipes are attached to such appliances on 
boilers, generators or engine, as are placed on such to receive 
them. 

All lap-welded iron or steel steam-pipes over 5 inches in diam- 
eter, or riveted wrought-iron or steel steam-pipes over 5 inches in 
diameter, in addition to being expanded into tapered holes and 
substantially beaded into recess* in face of flanges, as provided in 
preceding paragraph for steam and feed-pipes exceeding 2 inches 
and not exceeding 5 inches in diameter, shall be substantially and 



486 



HANDBOOK ON ENGINEERING. 



lirmly riveted, with good and substantial rivets, through the hubs 
of such flanges ; and no such hubs shall project from such flanges 
less than 2 inches in any case. 

Steam-pipes of iron or steel, when lap- welded by hand or 
machine, with their flanges welded on, shall be tested to a hydro- 
static pressure of at least double the working pressure of the 
steam to be carried and properly annealed after all the work 
requiring fire is finished. When an affidavit of the manufacturer 
is furnished that such test has been made and annealed, they may 
be used for marine purposes. 



WROUGHT IRON WELDED PIPE. 



GAS, 



DIMENSIONS, WEIGHTS, ETC., OF STANDARD SIZES FOR STEAM, 
WATER, OIL, ETC. 

1 inch and below are butt- welded, and tested to 300 pounds 
per square inch hydraulic pressure. 

IJ inch and above are lap-welded, and tested to 500 pounds 
per square inch hydraulic pressure. 



1 
si 


si 

13 OS 





Length of 1 
Pipe per sq. 1 
ft. of out- 1 
side surface.! 


a 53 

1^ 


"3 
?=s 


Length of 
Pipe con- 
taining one 
cubic foot. 


.£3 
S be 

_bCO 


1: 

=1-1 j^ « 

O A^ 


B 

Z So 


Weight of 
Water per 
foot of 
Length. 


Inch. 


Inches. 


Inches. 


Feet. 


Inches. 


Inches. 


Feet. 


Lbs. 






Lbs. 


i 


.40 


1.272 


9.44 


.012 


.129 


2500. 


.24 


27 


.0006 


.005 


i 


.54 


1.696 


7.075 


049 


229 


1.385. 


.42 


18 


.0026 


.021 




.67 


2.121 


5 657 


.110 


.358 


751.5 


.56 


18 


.0057 


.047 




84 


2.652 


4 502 


.196 


..5.54 


472.4 


.84 




.0102 


.085 


'. 


1.05 


3.299 


3.637 


.441 


.866 


270. 


1.12 




.0230 


.190 


1 


1 31 


4.134 


2.903 


.785 


1..3.57 


166.9 


1.67 


Hi 


.0408 


.349 


H 


1 66 


5.215 


2.. 301 


1.227 


2.164 


96.25 


2.25 




.0638 


.527 


i| 


1.9 


5.969 


2.01 


1.767 


2.835 


70.65 


2.69 




.0918 


.760 


2' 


2.. 37 


7.461 


1.611 


3.141 


4.430 


42.36 


3.66 


111 


.16.32 


1.356 


2| 


2.87 


9.032 


1.328 


4 908 


6.491 


,30.11 


5.77 


8 


.2550 


2.116 


3^ 


3 5 


10.996 


1 091 


7.068 


9.621 


19.49 


7.54 


8 


..3673 


3.049 


H 


4. 


12.566 


.9.55 


9.621 


12.566 


14.56 


9.05 


8 


.4998 


4.155 


i 


4.5 


14.137 


.849 


12.566 


15.904 


11.31 


10.72 


8 


.6528 


5.405 


H 


5. 


15.708 


,765 


15,904 


19.635 


9.03 


12.49 


8 


.8263 


6.851 


5" 


5.56 


17.475 


.629 


19.6.35 


24.299 


7.20 


14.56 


8 


1.020 


8.. 500 


6 


6.62 


20.813 


.577 


28.274 


34.471 


4.98 


18.76 


8 


1.469 


12.312 


7 


7.62 


23 954 


.505 


38.484 


45.663 


3.72 


23.41 


8 


1.999 


16.662 


H 


8 62 


27.096 


.444 


50.265 


58.426 


2.88 


28.34 


8 


2.611 


21.750 


9 


9 68 


30.4.33 


..394 


63.617 


73.715 


2., 26 


34.67 


8 


3.300 


27.500 


10 


10.75 


33.772 


..355 


78.540 


90,792 


1.80 


40.64 


8 


4.081 


34.000 



HANDBOOK ON ENGINEERING. 



487 



PULSATION IN STEAn=BOILERS. 



Palsation iu steam-boilers, though not discernible to the" eye, 
as in animated nature, goes on intermittently in some boilers 
whenever they are in use. It is induced by weakness and want 
of capacity in the boiler to supply the necessary quantity of 
steam, and sometimes is caused by the boiler being badly de- 
signed, thereby admitting of a great disproportion between the 
heating-surface and steam-room. Boilers are frequently found in 
factories that were originally not more than of sufficient capacity 
to furnish the necessary quantity of steam, but, as business 
increased, it became necessary to increase the pressure and also 
the speed of the engine; or, perhaps to replace it with a larger 
one, which has to be supplied with steam from the same boiler. 
The result is, each time the valve opens to admit steam to the 
cylinder, about one-third of the whole quantity in the boiler is 
admitted, thus lowering the pressure ; the next instant, under the 
influence of hard firing, or, perhaps, a forced draught, the steam 
is brought to the former pressure, and so on ; this lessening and 
increasing the pressure continues while the engine is in motion, 
which has an effect on the boiler similar to the breathing of an 
animal. 

The strains induced by this pulsation are transmitted to the 
weakest places, viz., the line of the rivet holes, and that marked 

by the tool in the process of 
calking ; the result is, the plate 
is broken in two, as shown in 
the above cut. The manner in 
which the break takes place 
may be illustrated by filing a 
small nick, or drilling a small 
hole, in a piece of hoop or band- 
iron, and then bending back 




488 



HANDBOOK ON ENGINEERING. 



and forth, when it will be discovered that the material will break 
just at that point, however slight the nick or small the hole may 
be. Pulsation is frequently very severe in the boilers of tug- 
boats when commencing to start a heavy tow, and also in loco- 
motives when starting long trains. Some frightful explosions of 
the boilers of tug-boats and locomotives have occurred under 
such circumstances. Pulsation, if permitted to continue, is sure 
to effect the destruction of the boiler. It is always made mani- 
fest by the vibrations of the pointers on steam gauges, or an 
unsteadiness in the mercury column. It may be remedied, to a 
certain extent, by adding a larger steam dome, but this has a 
tendency to weaken the boiler and render it more unsafe. The 
only sure preventive of such a silent and destructive agent is to 
have the boiler of sufficient capacity in the first place. 



WEIGHT OF SQUARE AND ROUND IRON PER LINEAR FOOT. 



SIDE 

OR 
DIAM. 


Weight, 


Weight, 


SIDE 

OR 
DIAM. 


Weight, 


Weight. 


SIDE 

OR 
DIAM. 


Weight, 


Weight, 


Square. 


Round. 


Square. 


Round. 


Square. 


Round. 


-A- 


.013 


.01 


2 


13.52 


10.616 


5 


84.48 


66.35 


i 


.053 


.041 


* 


15.263 


11.988 


i 


93.168 


73.172 


l\ 


.118 


.093 


k 


17.112 


13.44 


h 


102.24 


80.304 


i 


.211 


,165 


1 


19.066 


14.975 


I 


111.756 


87.776 


1 


.475 


.373 


h 


21.12 


16.588 








h 


.845 


.663 


1 


23.292 


18.293 


6 


121.664 


95.552 


1 


1.32 


1.043 


1 


25.56 


20.076 


I 


132.04 


103.704 


% 


1.901 


1.493 


i 


27.939 


21.944 


h 


142.816 


112.16 


I 


2.588 


2.032 


3 


30,416 


23.888 


i 


154.012 


120.96 


1 


8.38 


2.654 


i 


35.704 


28.04 


7 


165.632 


130.048 


i 


4.278 


3.359 


h 


41.408 


82.515 


I 


177.672 


139.544 


i 


5.28 


4.147 


f 


47.534 


37.332 


h 


190.136 


149.328 


i 


6.39 


5.019 








\ 


203.024 


159.456 


h 


7.604 


5.972 


4 


54.084 


42.464 








1 


8.926 


7.01 


k 


61.055 


47.952 


8 


216.336 


169.856 




10.352 


8.128 


h 


68.448 


53.76 








i 


11.883 


9 333 


1 


76.264 


59.9 


9 


273.792 


215.04 



HANDBOOK ON ENGINEERING. 489 

WATER COLUriNS. 

Every boiler should be equipped with a safety water column. 
Next to keeping the steam pressure within the limits of safety, 
the most important point to be observed in operating steam boilers 
is the maintenance of the proper water level. If the water level 
is too low, there is danger of burning the tubes and plates and^ 
perhaps, of wrecking the boiler ; if it is too high, water is liable to 
be carried, along with the steam and cause damage in the engine, 
while a constant variation in the water level produces a waste of fuel 
and unsteady pressure, and impairs the life of the boiler. Safety 
water columns have been devised for the purpose of insuring owners 
of steam boilers against accidents of this kind. They are so ar- 
ranged that any variation in the water level beyond reasonable lim- 
its will be loudly proclaimed by means of a suitable steam whistle. 

STEAM=QAUQES. 

The object of the steam-gauge is to indicate the steam pressure 
in the boiler, in order that it may not be increased far above that 
at which the boiler was originally considered safe ; and it is as. a 
provision against this contingency that a really good gauge is a 
necessity where steam is employed, for no guide at all is vastly 
better than a false one. The most essential requisites of a good 
steam-gauge are, that it be accurately graduated, and that the 
material and workmanship be such that no sensible deterioration 
may take place in the course of its ordinary use. The pecuniary 
loss arising from any considerable fluctuation of the pressure of 
steam has never been properly considered by the proprietors of 
engines. If steam be carried too high, the surplus will escape 
through the safety-valve, and all the fuel consumed to produce 
such excess is so much dead loss. On the other hand, if there be 
at any Jtime too little steam, the engine will run too slow, and 
every lathe, loom, or other machine driven by it, will lose its 
speed and, of course, its effective power in the same pro- 



490 HANDBOOK ON ENGINEERIN(4 . 

portion. A loss of one revolution in ten at once reduces the pro- 
ductive power of every machine driven by the engine ten per cent, 
and loses to the proprietor ten per cent of the time of every 
workman emj^loyed to manage such machine. In short, the loss 
of one revolution in ten diminishes the productive capacity of the 
whole concern ten per cent, so long as such reduced rate con- 
tinues ; while the expenses of conducting the shop (rent, wages, 
insurance, etc.) all run on as if everything was in full motion. 
A variation to this amount is a matter of frequent occurrence, 
and is, indeed, unavoidable, unless the engineer is afforded 
facilities to prevent it. A very little reflection will satisfy any 
one that it must be a very small concern, indeed, in which a half- 
hour's continuance of it would not produce a result more than 
enough to defray the cost of a very expensive instrument to pre- 
vent it. If the engineer, to avoid this loss, keeps a surplus of 
steam constantly on hand, he is constantly wasting the steam, 
and consequently, fuel, thus incurring another loss, which, 
though less alarming than the first, will yet be serious and render 
any instrument most desirable which can prevent it. It is, there- 
fore, of great importance to the proprietors of engines to have an 
instrument which can constantly indicate the pressure in the 
steam-boilers with accuracy. This would enable the engineer to 
keep his steam at a constant pressure, thus avoiding waste of fuel 
on the one hand, and the still more serious loss of the productive 
power of the shop on the other. An instrument, therefore, con- 
stantly indicating the pressure of steam, reliable in its character, 
and, with ordinary care, not subject to derangement, is evidently 
a desideratum both to the engineer and proprietor. The impor- 
tance of such an instrument, as a preventive of explosion, and of 
the frightful consequences to life and limb and ruinous pecuniary 
results of such disaster, is obvious on the slightest consideration ; 
but the value of the instrument, in the economical results of its 
daily use, is by no means properly appreciated. 



HANDBOOK ON ENGINEERING. 491 

SAFETY=VALVES. 

The form and construction of this indispensable adjunct to the 
steam boiler are of the highest importance, not only for the pres- 
ervation of life and property, which would, in the absence of that 
means of *' safety " be constantly jeopardized, but also to secure 
the durability of the steam-boiler itself. And yet, judging from 
the manner in which many things called safety-valves have been 
constructed of late years, it would appear that the true principle 
by which safety is sought to be secured by this most valuable ad- 
junct is either not well understood, or is disregarded by many 
engineers and boiler-makers. 

Boilet explosions have in many cases occurred when, to all 
appearances, the safety-valves attached have been in good work- 
ing -order; and coroners' juries have not unfrequently been 
puzzled, and sometimes guided to erroneous verdicts by scientific 
evidence adduced before them, tending to show that nothing was 
wrong with the safety-valves, and that the devastating catastro- 
phies could not have resulted from overpressure, because in such 
case the safety-valve would have prevented them. It is supposed 
that a gradually increasing pressure can never take place if the 
safety-valve is rightly proportioned and in good working order. 
Upon this assumption, universally acquiesced in, when there is no 
accountable cause, explosions are attributed to the "sticking" 
of the valves, or to " bent" valve-stems, or inoperative valve- 
springs. As the safety-valve is the sole reliance, in case of neg- 
lect or inattention on the part of the engineer or fireman, it is 
important to examine its mode of working closely. Safety-valves 
are usually provided with a spindle or guide-pin, attached to the 
under side, and passing through a cross-bar within the boiler, 
directly under the seating of the valve, which may be seen in 



492 



HANDBOOK ON ENGINEERING. 



the cut below. Now, it is evident that if this guide-pin 
becomes bent from careless handling, the safety-valve may 
be rendered almost inoperative, and, instead of releasing the 
pressure at the point indicated, it will turn sideways, 
and allow only a small aperture for the escape of steam, 
and, further, it will not return perfectly to its seat; 
hence, a leaky valve is the result, and to overcome this difficulty, 
ignorant engineers and firemen generally resort to extra weight- 
ing ; and it is not uncommon to find double or treble the weight 




corresponding to the pressure required in the boiler. Another 
difficulty is that the safety-valve levers sometimes get bent, and 
the weight, consequently, hangs on one side of the true center ; 
this, it will be seen, causes the valve to rest more heavily on one 
side than on the other, and the greater the added weight the 
greater the difficulty. The seats of safety-valves should be 
examined frequently to see that no corrosion has commenced ; as 
valves, especially if leaky, become corroded and often stick fast, 
so that no little force is required to raise them. If, when a 
safety-valve is properly weighted, it should be found leaking, do 
not put on extra weights, but immediately make an examination, 
and in all probability the seat or guide-pin will be found cor- 
roded, or there will be foreign matter between the valve and its 



HANDBOOK ON ENGINEERING. 493 

seat. By taking the lever in the hand and raising- it from its seat 
a few times, any substance that may have kept it from its seat 
will be dislodged ; or it may turn out on examination that the 
lever had deviated from some cause from a true center. Such 
difficulties can be easily righted, but extra weight should never be 
added, as it only aggravates the trouble instead of remedying it. 
When the weight of the safety-valve is set on the lever at safe 
working pressure, or at the distance from the fulcrum necessary 
to maintain the pressure required to work the engine, any 
extra length of lever should then be cut off as a precaution, 
to prevent the moving out of the weight on the lever, for the 
purpose of increasing the pressure, as, while the lever remains 
sufficiently long, the weight can be increased to a dangerous 
extent without attracting any attention ; while if the lever is cut 
off at the point at which the safe working |)ressure is designated, 
any extra increase of pressure can only be accomplished by add- 
ing more weight to the lever, which is tolerably sure to attract the 
attention of some one interested in the preservation of the lives 
and property of persons in the immediate vicinity. 

The bolts that form the connection between the lever, fulcrum 
and valve-stem should be made of brass, in order to prevent the 
possibility of corrosion, " sticking " or becoming magnetized, as 
it is termed ; and for the same reason, the valve and seat should 
be made of two different metals. When safety valves become 
leaky they should be taken out and reground on their seats, for 
which purpose pulverized glass, flour of emery, or the fine grit or 
mud from grinding stone troughs are the most suitable material ; 
but whether they leak or not, they should be taken apart at least 
once a year and all the working parts cleaned, oiled and read- 
justed. The safety-valve is designed on the assumption that it 
will rise from its seat under the statical pressure in the boiler, 
when this pressure exceeds the exterior pressure on the valve, and 
that it will remain off its seat sufficiently far to permit all the 



494 HANDBOOK ON ENGINEERING. 

steam which the boiler can produce to escape around the edges of 
the valve. The problem then to be solved is : What amount of 
opening is necessary for the free escape of the steam from the 
boiler under a given pressure? The area of a safety-valve 
is generally determined from formulae based on the velocity 
of the flow of steam under different pressures, or upon the 
results of experiments made to ascertain the area necessary for 
the escape of all the steam a boiler could produce under a given 
pressure. But as the fact is now generally recognized by 
engineers that valves do not rise appreciably from their seats 
under varying pressures, it is of importance that in practice 
the outlets round their edges should be greater than those based 
on theoretical considerations. The next point to be considered is 
how high any safety valve will rise under the influence of a given 
pressure. This question cannot be determined theoretically, but 
has been settled conclusively by Burg, of Vienna, who made 
careful experiments to determine the actual rise of safety-valves 
above their seats. His experiments show that the rise of the 
valve diminishes rapidly as the pressure increases. 

TABLE SHOWING THE RISE OF SAFETY-VALVES, IN PARTS OF AN 
INCH, AT DIFFERENT PRESSURES. 

Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. Lbs. 
12 20 35 45 50 60 70 80 90 



Taking ordinary safety-valves, the average rise for pressures 
from 10 to 40 pounds is about jL of an inch^ from 40 to 70 
pounds about gL, and from 70 to 90 pounds about yj^ of an 
inch. The following table gives the result of a series of experi- 
ments made at the Novelty Iron Works, New York, for the pur- 
pose of determining the exact area of opening necessary for 



HANDBOOK ON ENGINEERING. 



495 



safety-valves, for each square foot of heating surface, at different 
boiler pressures. 




TABLE OF COMPAKISON BETWEEN EXPERIMENTAL RESULTS AND 
THEORETICAL FORMULAE. 



Boiler Pressure, 45 pounds. 


Boiler Pressure, 75 pounds. 


TTontino- ^^^^^ ^f Open- 

?urfac# ing found by 
ouiidce. experiment. 


Area of open- 
ing according 
to formulae. 


Heating 
Surface. 


Area of open- 
ing found by 
experiment. 


Area of open- 
ing according 
to formulae. 


! 

Sq. Ft.i Sq. Ins. 

100 .089 

200 , .180 

500 .45 

1000 ' .89 

2000 ! 1.78 

5000 4.46 


Sq. Ins. 
.09 
.19 
.48 
.94 
1.90 
4.75 


Sq. Ft. 

100 

200 

500 
1000 
2000 
5000 


Sq. Ins. 

.12 

.24 

.59 
1.20 
2.40 
6.00 


Sq. Ins. 

.12 

.24 

.59 
1.18 
2.37 
5.95 



496 HANDBOOK ON ENGINEERING. 

Now^ if we compare the area of openings, according to these 
experiments, with Zeuner's formula, which is entirely theoretical, 
it will be observed that the results from the two sources are 
almost identical, or so nearly so as not to make any material 
difference. In the absence of any generally recognized rule, it 
is customary for engineers and boiler-makers to proportion safety- 
valves according to the heating surface, grate-surface, or horse- 
power of the boiler. While one allows one inch of area of 
safety-valve to QQ square feet of heating surface, another gives 
one inch area of safety-valve to every four horse power ; while a 
third proportions his by the grate-surface — it being the custom 
in such cases to allow one inch area of safety-valves to 2 square 
feet of grate-surface. This latter proportion has been proved by 
long experience and a great number of accurate experiments, to 
be capable of admitting of a free escape of steam without allowing 
any material increase of the pressure beyond that for which the 
valve is loaded, even when the fuel is of the best quality, and the 
consumption as high as 24 pounds of coal per hour per square 
foot of grate-surface, providing, of course, that all the parts are 
in good working order. It is obvious, however, that no valve 
can act without a slight increase of pressure, as, in order to lift 
at all, the internal pressure must exceed the pressure due to the 
load. 

The lift of safety-valves, like all other puppet-valves, de- 
creases as the pressure increases ; but this seeming irregularity is 
but what might be required of an orifice to satisfy appearances in 
the flow of fluids, and may be explained as follows : A cubic foot 
of water generated into steam at one pound pressure per square 
inch above the atmosphere, will have a volume of about 1,600 
cubic feet. Steam at this pressure will flow into the atmosphere 
with a velocity of 482 feet per second. Now, suppose the steam 
was generated in five minutes, or in 300 seconds, and the area of 
an orifice to i3ermit its escajDe as fast as it is generated be re- 



HANDBOOK ON ENGINEERING. 497 

quired, 1600 divided by 482 x 300 will give the area of the orifice, 
1| square inches. If the same quantity of water be generated into 
steam at a pressure of 50 pounds above the atmosphere, it will 
possess a volume of 440 cubic feet and will How into the atmos- 
phere with a velocity of 1791 feet per second. The area of an 
orifice, to allow this steam to escape in the same time as in the 
first case, may be found by dividing 440 by 1791x300, the 
result will be ^^ square inches, or nearly i of a square inch, the 
area required. It is evident from this that a much less lift of the 
same valve will suffice to discharge the same weight of steam 
under a high pressure than under a low one, because the steam 
under a high pressure not only possesses a reduced volume, but a 
greatly increased velocity ; it is also obvious from these consider- 
ations, that a safety-valve, to discharge steam as fast as the boiler 
can generate it, should be pioportioned for the lowest pressure. 

RULES. 

Rule* — For finding the weight necessary to put on a safety- 
valve lever when the area of valve, pressure, etc., are known: 
Multiply the area of valve by the pressure in pounds per square 
inch ; multiply this product by the distance of the valve from the 
fulcrum ; multiply the weight of the lever by one-half its length 
(or its center of gravity) ; then multiply the weight of valve and 
stem by their distance from the fulcrum ; add these last two prod- 
ucts together, subtract their sum from the first product, and 
divide the remainder by the length of the lever ; the quotient will 
be the weight required. 



EXAMPLE. 



Area of valve, 12 in. 
Pressure, 65 lbs. 



Fulcrum, 4 in. . 



65 


13 


8 


12 


16 


4 


80 


208 


32 



498 HANDBOOK ON ENGINEERING. 

Length of lever, 32 in 4 13 

Weight of lever, 13 lbs 

Weight of valve and stem, 8 lbs 3120 208 

240 32 



32)2880 240 
90 lbs. 

Rule for finding the pressure per square inch when the area of 
valve, weight of ball, etc., are known: Multiply the weight of ball 
by length of lever, .and multiply the weight of lever by one-half its 
length (or its center of gravity) ; then multiply the weight of 
valve and stem by their distance from the fulcrum. Add these 
three products together. This sum, divided by the product of 
the area of valve, and its distance from the fulcrum, will give the 
pressure in pounds per square inch. 

EXAMPLE. 

Area of valve, 7 in . 50 12 6 

Fulcrum, 3 in 30 15 3 

Length of lever, 30 in 1500 180 18 

Weight of lever, 12 lbs 180 

Weight of ball, 50 lbs. ....... 18 7 

Weight of valve and stem, 6 lbs 

21)1698 3 

80.85 lbs. 21 

Rule for finding the pressure at which a safety-valve is 
weighted when the length of the lever, weight of ball, etc., are 
known : Multiply the length of lever in inches by the weight of 
ball in pounds ; then multiply the area of valve by its distance 



HANDBOOK ON ENGINEERING. 499 

from the fulcrum ; divide the former product by the latter ; the 
quotient will be the pressure in pounds per square inch. 

EXAMPLE. 

Length of lever, 24 in 52 7 

Weight of ball, 52 lbs 24 3 

Fulcrum, 3 in 208 21 

Area of valve, 7 in 104 

21)1248 

59.42 lbs. 

The above rule, though very simple, cannot be said to be 
exactly correct, as it does not take into account the weight of the 
lever, valve and stem. 

Rule for finding center of gravity of taper levers for safety- 
valves : Divide the length of lever by two (2); then divide 
the length of lever by six (6), and multiply the latter quotient 
by width of large end of lever less the width of small end, 
divided by width of large end of lever plus the width of small end. 
Subtract this product from the first quotient, and the remainder 
will be the distance in inches of the center of gravity from large 
end of lever. 

EXAMPLE. 

Length of lever 36 in. 

Width of lever at large end .......... 3 " 

Width of lever at small end . . . 2 " 

36 divided by 2 = 18 minus 1.2 = 16.8 in. 36 divided by 6 = 
6X1=6 divided by 5 = 1.2. 

Center of gravity from large end, 16.8 in. 

The safety-valve has not received that attention from engi- 
neers and inventors which its importance as a means of safety 



500 HANDBOOK ON ENGINEERING. 

SO imperatively deserves. In the constructiou of most other 
kinds of machinery, continual efforts have been made to secure 
and insure accuracy ; while in the case of the safety-valve, very 
little improvement has been made either in design or fitting. It 
is difficult to see why this should be so, when it is known that 
deviations from exactness, though trifling in themselves, when 
multiplied, not only affect the free action and reliability of 
machines, but frequently result in serious injury, more partic- 
ularly in the case of safety-valves. 

Safety- valves should never be made with rigid stems, as, in 
consequence of the frequent inaccuracy of the other parts, the 
valve is prevented from seating, thereby causing leakage ; as a 
remedy for which, through ignorance or want of skill, more 
weight is added on the lever, which has a tendency to bend 
the stem, thus rendering the valve a source of danger instead 
of a means of safety. The stem should, in all cases, be fitted 
to the valve with a ball and socket joint, or a tapering stem 
in a straight hole, which will admit of sufficient vibration to 
accommodate the valve to its seat. It is also advisable that 
the seats of safety-valves, or the parts that bear, should be as 
narrow as circumstances will permit, as the narrower the seat 
the less liable the valve is to leak, and the easier it is to repair 
when it becomes leaky. 

AH compound or complicated safety-valves should be avoided, 
as a safety-valve is, in a certain sense, like a clock — any 
complication of its parts has a tendency to affect its reliability 
and impair its accuracy. 

It has been too much the custom heretofore for owners of steam 
boilers to disregard the advice and suggestions of their own en- 
gineers and firemen, even though men of intelligence and experi- 
ence, and to be governed entirely by the advice of self-styled 
experts and visionary theorists, 



HANDBOOK ON ENGINEERING. 501 

Table of Heating Surface in Square Feet, 



Diam. of Boiler in inches 


24 


1 
30 32 


34 


36 


38 


40 


42 


44 


48 


f Heating surface of sliell 
per foot of length. 


4.19 


5.24 


5.57 


5.93 


6.28 


6.63 


6.98 7.73 


7.68 


8.38 


Diameter of Tube or Flue 
in inches. 


2 


2i 


3 


sh 


4 


ih 


5 


6 


7 


8 


Whole External Heating 
surface per foot length. 


.524 


.655 


.785 


.916 


1.05 


1.18 


1.31 1.57 


1.83 2.09 



60 


52 


54 


56 


58 


60 


62 


64 


66 


68 


70 


72 


8.73 


9.08 


9.42 


9.77 


10.12 


10.47 


10.82 


11.17 


11.52 


11.87 


12.22 


12.57 


9 


10 


11 


12 


13 


14 


15 


16 


17 


18 


19 


20 


'Z.BB 


2.62 


2.88 


3.14 


3.40 


3.66 


3.93 


4.19 


4.45 


4.71 


4.96 


5.24 



CENTRIFUGAL FORCE. 



The centrifugal force of a body depends upon its weight Win 
pounds ; distance B in feet it is from the center of rotation, and 
the number of revolutions N it makes about that center each 

WR N^- 
minute and equals — oqoo — • 

Multiply the weight in pounds by radius in feet, by square 
of number of revolutions, and divide by 2933 = centrifugal force 
in pounds. 



502 HANDBOOK ON ENGINEERING. 



CHAPTER XVIII. 
THE WATER TUBE SECTIONAL BOILER. 

The water tube sectional boiler has been a growth of many 
years and of many different minds. There are some two and a 
half million horse-power in daily service in the United States 
alone, and the number is rapidly increasing. Large orders for 
this type of boiler have often been repea?ted, adding proof that its 
principles are correct and appreciated by those having them in 
use and in charge. This being the case, purchasers should note 
well the points of difference in the various water tube boilers 
claiming their attention, and particularly see that the claims 
made for them are embodied in their actual construction. The 
general principles of construction and operation of this class of 
steam boilers are now well known to engineers and steam users. 
In selecting a water tube boiler there are several vital points to 
be considered : — 

1st. Straight and smooth passages through the headers of ample 
area, insuring rapid and uninterrupted circulation of the water. 

2d. The baffling of the gases (without throttling or impeding 
the circulation of the water) in such a way that they are com- 
pelled to pass over every portion of the heating surface. 

3d. Sufficient liberating surface in the steam drums to 
insure dry steam, with large body of water in reserve to draw 
from. 

4th. A steam reservoir or steam drum. 

5th. Simplicity in construction ; accessibility for cleaning and 
inspection. 

6th. A header, which in its design provides for the unequal 
expansion and contraction. 



HANDBOOK ON ENGINEERING. 



503 




Illustration above is that of a Horizontal Safety Water Tube 
Boiler, manufactured by the John O'Brien Boiler Works Company, 
of St. Louis, U. S. A. 



Down draft f urnace* — A great many of these boilers are fit- 
ted with the down draft furnaces, and the above illustration shows 
the style of same, together with the manner in which they are 
connected. 

A full and complete description of these furnaces is given on 
page 522. 

Description^ — In construction, this type of boiler consists 



504 HANDBOOK ON ENGINEERINf4. 

simply of a front and rear water leg or header, made approx- 
imately rectangular in shape, overhead combination steam and 
water drum or drums and with circulating water tubes, as 
shown in cut, which extend between and connect both front and 
rear headers, being thoroughly expanded into the tube sheets. 
The tubes are inclined on a pitch of one inch to the foot and, the 
rear header being longer than the front one, the overhead drum 
connecting both headers lies perfectly level when the boiler is set 
in position. The connection of the headers with the combined 
steam and water drum is made in such a manner as to give prac- 
tically the same area as the total area of the tubes, so there is no 
contraction of area in the course of circulation ; and extending 
between and connecting the inside faces of the water legs, 
which form end connections between these tubes and the com- 
bined steam and water drums or shells, placed above and parallel 
with them, also a steam drum above these, assures absolutely dry 
steam and a large steam space, also a large water space. The water 
legs are made larger at the top, about 11 inches wide, and at the 
bottom about 7 inches wide, which is a great advantage, allowing 
the globules of steam to pass quickly up the water legs to the 
steam and water drums. The water, as it sweeps along the 
drums, frees itself of steam ; then it goes down the back connec- 
tion until it meets the inclined tubes, meeting on its passage a 
gradually increasing temperature, till the furnace is again reached, 
where the steam formed on the way is directly carried up in the 
drum as before. The tubes extend between and connect both the 
front and rear headers and are thoroughly expanded into the 
tube sheets. Opposite the end of each tube there is an oval 
hand-hole slightly larger than the tube proper through which it 
can be withdrawn. It will be noted that the throat of each 
water leg is li times the total tube area. The rapid and 
unimpeded circulation tends to keep the inside surface clean and 
floats the scale-making sediment along until it reaches the back 



HANDBOOK ON ENGINEERING. 



505 



water leg, where it is carried down and settles in the bottom of leg, 
where it is blown off at regular intervals. 




Steadiness of water leveL — The large area of surface at water 
line and the ample passages for circulation, secure a steadiness 



50G HANDBOOK ON ENGINEERING. 

of water level unsurpassed by any boiler. This is a most im- 
portant point in boiler construction and should always be consid- 
ered when comparing boilers. The water legs are stayed by hol- 
low stay-bolts of hydraulic tubing of large diameter, so placed that 
two stays support each tube and hand-hole and are subjected to only 
very slight strain. Being made of heavy material, they form the 
strongest parts of the boiler and its natural supports. The water 
legs are joined to the shell by flanged and riveted joints and the 
drum is cut away at these two points to make connection with in- 
side of water leg, the opening thus made being strengthened by 
special stays, so as to preserve the original strength. The shells 
are cylinders with heads dished to form part of a true sphere. 
The sphere is everywhere as strong as the circular seam of the 
cylinder, which is well known to be twice as strong as the side 
seam ; therefore, the heads require no stays. Both the cylinder 
and the spherical heads are, therefore, free to follow their natural 
lines of expansion when put under pressure. 

The illustration on page 505 plainly shows the formation of 
the front water leg or header in this type of water tube boiler. 

It will be seen that the hand plates are all oval in shape, allow- 
ing each one to be removed from its respective hole ; also, the 
manner of bracing with hollow stay-bolts is shown. 

Note that the feed pipes for supplying furnace are equipped 
with oval hand plates to facilitate cleaning. 

Walling" in* — In setting the boiler, its front water leg is placed 
firmly on a set of strong, cast-iron columns bolted and braced to- 
gether by the door frames and dead-plates and forming the fire 
front. This is the fixed end. The rear water legs rest on rollers 
which are free to move on cast-iron plates firmly set in the ma- 
sonry of the low and solid rear wall. Thus the boiler and its walls 
are each free to move separately during expansion or contraction, 
without loosening any joints in the masonry. 

On the lower, and between the upper tubes, are placed light 



HANDBOOK ON ENGINEERING. 507 

fire-brick tiles. The lower tier extends from the front water leg 
to within a few feet of the rear one, leaving there an upward pass- 
age across the rear ends of the tubes for the flame. The upper 
tier closes into the rear water leg and extends forward to within 
a few feet of the front one, thus leaving an opening for the gases 
in front. The side tiles extend from side walls to tile bars and 
close up to the front water leg and front wall, and leave open the 
final uptake for the waste gases. 

The gases being thoroughly mingled in their passage between 
the staggered tubes, the combustion is more complete, and the 
gases impinging against the heating surface perpendicularly, in- 
stead of gliding along the same longitudinally, the absorption of 
the gas is more thorough. The draft area, being much 
larger than in fire tube boilers, gives ample time for the 
absorption of the heat of the gases before their exit to the 
chimney. 

DESCRIPTION OF THE HEINE SAFETY BOILER. 

The boiler is composed of lap-welded wrought-iron tubes ex- 
tending between and connecting the inside faces of two ' ' water 
legs," which form the end connections between these tubes and 
a combined steam and water drum or " shell " placed above and 
parallel with them. (Boilers over 200 horse-power have two such 
shells.) These end chambers are of approximately rectangular 
shape, drawn in at top to fit the curvature of the shells. Each is 
composed of a head plate and a tube sheet flanged all around 
AND JOINED AT BOTTOM and sides by a butt strap of same material, 
strongly riveted to both. The water legs are further stayed by 
hollow stay-bolts of hydraulic tubing of large diameter, so placed 
that two stays support each tube and hand-hole and are subjected 
to only very slight strain. Being made of heavy metal, they form 
the strongest parts of the boiler and its natural supports. The 



508 



HANDBOOK ON ENGINEERING. 



water legs are joined to the shell by flanged and riveted joints, 
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with inside of water leg, the opening thus made being strength- 
ened by bridges and special stays so as to preserve the original 
strength. 



HANDBOOK ON ENGINEERING. 509 

The shells are cylinders with heads dished to form parts of a 
true sphere. The sphere is everywhere as strong as the circle 
seam of the cylinder, which is well known to be twice as strong as 
its side seam. Therefore, these heads require no stays. Both 
the cylinder and its spherical heads are, therefore, free to follow 
their natural lines of expansion when put under pressure. Where 
flat heads have to be braced to the sides of the shell, both suffer 
local distortions where the feet of the braces are riveted to them, 
making the calculations of their strength fallacious. This they 
avoid entirely by their dished heads. To the bottom of the front 
head a flange is riveted, into which the feed-pipe is screwed. 
This pipe is shown in the cut with angle valve and check valve 
attached. On top of shell, near the front end, is riveted a steam 
nozzle or saddle, to which is bolted a tee. This tee carries the steam 
valve on its branch, which is made to look either to front, rear, 
right or left ; on its top the safety valve is placed. The saddle 
has an area equal to that of stop valve and safety valve combined. 
The rear-head carries a blow-off flange of about same size as the 
feed flange, and a manhead curved to flt the head, the manhole 
supported 'by a strengthening ring outside. On each side of the 
shell a square bar,- the tile-bar, rests loosely in flat hooks riveted 
to the shell. This bar supports the side tiles, whose other ends 
rest on the side walls, thus closing the furnace or flue on top. 
The top of the tile-bar is two inches below low water line. The 
bars rise from front to rear at the rate of one inch in twelve. 
When the boiler is set, they must be exactly level, the whole 
boiler being then on an incline, i. e., with a fall of one inch in 
twelve from front to rear. It will be noted that this makes the 
height of the steam space in front about two-thirds the diam- 
eter of the shell, while at the rear the water occupies two-thirds 
of the shell, the whole contents of the drum being equally divided 
between steam and water. The importance of this will be eX' 
plained hereafter. 



510 



HAJ^DBOOK ON ENGINEERING. 



The tubes extend through the tube sheets, into which they are 
expanded with roller expanders ; opposite the end of each and in 
the head-plates, is placed a hand -hole of slightly larger diam- 




eter than the tube, and through which it can be withdrawn. 
These hand-holes are closed by small cast-iron hand -hole plates, 
which, by an ingenious device for locking, can be removed in a 



HANDBOOK ON ENGINEERING. 511 

few seconds to inspect or clean a tube. The accompanying cut 
shows these hand-hole plates marked H. In the upper corner 
one is shown in detail, H'^ being the top view, H^ the side view 
of the plate itself, the shoulder showing the place for the gasket. 
.H^ is the yoke or crab placed outside to support the bolt and nut. 
Inside of the shell is located the mud drum D, placed well 
below the water line, usually parallel to and 3 inches above the 
bottom of the shell. It is thus completely immersed in the hot- 
test water in the boiler. It is of oval section, slightly smaller 
than the manhole, made of strong sheet-iron with cast-iron heads. 
It is entirely inclosed except about 18 inches of its upper 
portion at the forward end, which is cut away nearly parallel to 
the water line. Its action will be explained below. The feed- 
pipe F enters it through a loose joint in front ; the blow-off pipe 
^ is screwed tightly into its rear-head, and i^asses by a steam- 
tight joint through the rear-head of the shell. Just under the 
steam nozzle is placed a dry pan or dry pipe A. A deflection 
plate L extends from the front head of the shell, inclined up- 
wards, to some distance beyond the mouth or throat of the front 
water leg. It will be noted that the throat of each water leg is 
large enough to be the practical equivalent of the total tube area, 
and that just where it joins the shell it increases gradually in 
width by double the radius of the flange. 

Erection and walling" in. — In setting the boiler, its front 
water leg is placed firmly on a set of strong cast-iron columns, 
bolted and braced together by the door frames, deadplate, etc., 
and forming the fire front. This is the fixed end. The rear 
water leg rests on rollers, which are free to move on cast-iron 
plates firmly set in the masonry of the low and solid rear wall. 
Wherever the brickwork closes in to the boiler, broad joints are 
left which are filled in with tow or waste saturated with fireclay, 
or other refractory but pliable material. Thus the boiler and its 
walls are each free to move separately during expansion or con- 



512 HANDBOOK ON ENGINEERING. 

traction without loosening any joints in the masonry. On the 
lower, and between the upper tubes, are placed light fire-brick 
tiles. The lower tier extends from the front water leg to within 
a few feet of the rear one, leaving there an upward passage across 
the rear ends of the tubes for the flame, etc. The upper tier 
closes in to the rear water leg and extends forward to within a 
few feet of the front one, thus leaving the opening for the gases in 
front. The side tiles extend from side walls to tile bars and close 
up to the front water leg and front wall, and leave open the final 
uptake for the waste gases over the back part of the shell, which 
is here covered above water line with a rowlock of firebrick rest- 
ing on the tile bars. The rear wall of the setting and one paral- 
lel to it arched over the shell a few feet forward, form the uptakes. 
On these and the rear portion of the side walls is placed a light 
sheet-iron hood, from which the breeching leads to the chimney. 
When an iron stack is used, this hood is stiffened by L and T 
irons so that it becomes a truss carrying the weight of such stack 
and distributing it to the side walls. 

Longitudinal section of Heine Boiler and its operation* — 
The boiler being filled to middle water line, the fire is started on 
the grate. The flame and gases pass over the bridge wall and 
under the lower tier of tiling, finding in the ample combustion 
chamber space, temperature and air supply for complete combus- 
tion, before bringing the heat in contact with the main body of the 
tubes. Then, when at its best, it rises through the spaces be- 
tween the rear ends of the tubes, between rear water leg and back 
end of the tiling, and is allowed to expand itself on the entire 
tube heading surface without meeting any obstruction. Ample 
space makes leisurely progress for the flames, which meet in turn 
all the tubes, lap round them, and finally reach the second uptake 
at the forward end of the top tier of tiling, with their temperature 
reduced to less than 900^ Fahrenheit. This has been measured 
here, while wrought iron would melt just above the lower tubes at 



HANDBOOK ON ENGINEERING. 



513 



rear end, showing a reduction of temperature of over 1,800^ Fahr. 
between the two points. As the space is studded with water 
tubes, swept clean by a positive and rapid circulation, the absorp- 
tion of this great amount of heat is explained. The gases next 
travel under the bottom and sides of shell and reach the uptake 
at just the proper temperature to produce the draft required. 
This varies, of course, according to chimney, fuel required, etc. 
With boilers running at their rated capacity, 450° Fahrenheit are 




A furnace that is used in the East a o;reat deal. 



seldom exceeded. Meanwhile, as soon as the heat strikes the 
tubes, the circulation of the water begins. The water nearest the 
surface of the tubes becoming warmer, rises, and as the tubes are 
higher in front, this water flows towards the front water leg 
where it rises into the shell, while colder water from the shell 
falls down the rear water leg to replace that flowing forward and 
upward through the tubes. This circulation, at first slow, in- 



514 



HANDBOOK ON ENGINEEEING. 



creases in speed as soon as steam begins to form. Then the 
speed with which the mingled current of steam and water rises in 
the forward water leg will depend on the difference in weight of 
this mixture, and the solid and slightly colder water falling down 
the rear water leg. The cause of its motion is exactly the same 
as that which produces^draft in a chimney. 



Plain Vertical Tubular BdIc^ 




This cut shows the place for gauge cocks and water glass in an 
upright boiler. 



HANDBOOK ON ENGINEERING. 



515 




The above cut shows the water-column in its proper place. 



516 



HANDBOOK ON ENGINEERING. 



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520 



HANDBOOK ON ENGINEERING. 




-13'- 



e'^6%' 



J6 



The above cut shows the proper j^lace for closing in the boiler 
on the side — also the space between side of boiler 
and side walls. 



PIANDBOOK ON ENGINEERING. 



521 




Tlie above cut shows the proper place for gauge-cocks in a 
submerged tube boiler. 



522 



HANDBOOK ON ENGINEERING. 



THE AMOUNT OF MATERIAL REQUIRED TO BRICK 
UP BOILERS OF DIFFERENT SIZE. 





VI . 


ik 


6 >i O 








O „^^ .^^ 


"S3 
.2 o 






Fire Bri 
Eire Cla 

lb. to 
each bri 


6 

a 


6 6 


li 


Cement f 

concrete 

footing 2 

and 2 ft 

thick und 
all walls 


72"x22' 


18" 


10,500 


2,500 


18 bu. 


88 


8 


9bbl. 


72"x20' 


18" 


10,000 


2,300 


18 bu. 


80 


8 


8bbl. 


72"xl8' 


18" 


9,500 


2,200 


17 bu. 


72 


7 


8bbl. 


60"x20' 


18" 


9,500 


2,200 


17 bu. 


80 


7 


8bbl. 


60"xl8' 


18" 


9,000 


2,000 


16 bu. 


72 


7 


8bbL 


54"x20' 


18" 


8,700 


1,900 


15 bu. 


80 


6 


8bbl. 


54"xl8' 


18" 


8,000 


1,800 


15 bu. 


72 


6 


Sbbl. 


54"xl6' 


18" 


7,500 


1,700 


14 bu. 


64 


6 


7bbl. 


48"xl8' 


18" 


7,500 


1,600 


14 bu. 


72 


6 


7bbl. 


48"xl6' 


18" 


7,200 


1,500 


14 bu. 


64 


5 


7bbL 


42"xl8' 


18" 


7,000 


1,400 


12 bu. 


72 


5 


7bbL 


42"xl6' 


18" 


6,500 


1,300 


12 bu. 


64 


4 


7bbl. 



If 13" wall \ less on Red Brick. 

THE DOWN DRAUGHT FURNACE. 

The down draught furnace is noted for being one of the best 
smoke preventing furnaces in the market, while at the same time 
the cheapest kind of coal can be used. 

The down draught furnace made a good smoke record, even 
with overworked boilers, doing variable work, and with a marked 
economy in fuel. My experience with the down draught furnace, 
I feel safe in saying that smoke from boiler furnaces can now be 
abated by practical means, without hardship, no matter what the 
type of boiler. 

Directions for firingf the Down Draug^ht Furnace^ — When 
firing the furnace, throw the coal evenly over the entire grate 
surface, from 6 to 8 inches in depth, a little heaviest at the 
rear end of the furnace. Do not put in too much coal — 
burn more air ; and economize with your fuel and 



HANDBOOK ON ENGINEERING. 



523 



do not pile up the coal in front near the door. Never fire any 
fresh coal on the lower grates ; let in air below the lower grates. 
When poking the lire, run the slice-bar down between the water 
grates and back the full length of the grates ; then raise the slice- 
bar and gently shake the coal, and then pull it out without stir- 
ring up the fire. Never turn the fire over so that black coal gets 
down upon the water grates, unless there is a large clinker to re- 
move. Never give 'the top grates a general cleaning, so as to 
leave a portion of the grates uncovered and the remainder with a 
hot fire on them, as this causes an uneven expansion in the differ- 
ent tubes forming the water grates, and is liable either to bend 
the tubes or strip off the threads where they enter the drums. 
When the top fire becomes clogged with clinkers so that you can- 




Down Draught Furnace. 



not keep up steam, run in the slice-bar and raise the clinkers to 
the top of the fire ; remove the large clinkers, leave the small ones 
alone, and put on afresh fire. The lower grates must have proper 



524 



HANDBOOK ON ENGINEERING. 



attention. The coals must be raked over evenly and all holes 
filled up, particular care being taken that the grates are perfectly 
covered all over. If considerable coals have accumulated on the 




View of the Down Draught Furnace. 

lower grates and the air spaces are closed with ashes or clinkers, 
the slice-bar must be used and the clinkers raised up and turned 
over and the larger ones removed. It is best to remove the clink- 
ers every two or three hours, leaving the coals to burn up. 



SPECIFICATIONS FOR ONE SIXTY=INCH HORIZONTAL 
INCH FLUE BOILER. 



SIX= 



General directions, — There will be one boiler 20 feet long from 
out to out of heads and 60 inches inside diameter. 

Material, quality, thickness, etc. — Material in shell of the 
above named boiler to be made of homogeneous flange steel -f^" 
thick, having a tensile strength of not less than 60,000 lbs. to 



HANDBOOK ON ENGINEEKING. 



525 




526 HANDBOOK ON ENGINEERING. 

the square inch of section, with not less than 56 per cent ductil- 
ity, as indicated by contraction of area at point of fracture under 
test, or by an elongation of 25 per cent in length of 8 inches. 
Heads must be i" thick and of the same quality of steel as that 
in the shell. All plates and heads must be plainly stamped with 
the maker's name, and tensile strength. 

Tubes, sizCf number and arrangement* ^ The boiler must 
contain 18-6" lap- welded flues, riveted to the heads with Ten |" 
rivets in each head ; said flues must be made of charcoal iron of the 
best American make, standard thickness, equal to the National 
Tube Works Company's make. All flues must have at least 3 
inch clear space between them, and not less than 3 inches 
between flues and shell. All flanging of heads must be free from 
flaws or cracks of any description, and properly annealed in an 
annealing oven before riveting to the boiler. If 4-inch flues are 
wanted in place of 6 -inch, the boiler must have 44 best lap- 
welded tubes, 4" in diameter and 20 feet long, set in vertical and 
horizontal rows, with a clear space between them, vertically and 
horizontally of l^", except the central vertical space, which is to 
be 4 inches. Holes for tubes to be neatly chamfered off on the 
outside. Tubes to be set with a Dudgeon expander, and beaded 
down at each end. 

Riveting, — The longitudinal seams of the boiler must be 
above the fire line, and have a triple row of rivets ; all rivets to 
be I" in diameter ; and all rivets to be of sufficient length to 
form upheads equal in size to the pressed heads of same. The 
rivets in the longitudinal seams must be spaced 3i" apart 
from center to center, and the rows of same to be pitched 2^^" 
apart from center to center, so as to give an efficiency of the 
joint of -^^^ per cent of the solid plate. Transverse seams to 
be single riveted with same size rivets as those in the longitudinal 
seams pitched 2" apart from center to center. Care must be 
taken in punching and drilling holes that they may come fair in 



HANDBOOK ON ENGINEERING. 527 

construction ; the use of a drift-pin to bring blind, or partially 
blind holes in line will be sufficient cause for the rejection of 
the boiler. 

Calking. — The edges of the plates to be planed and beveled 
before making up the boilers, and the calking to be done with 
round nose tools, pneumatically driven ; no split or wedge calk- 
ing will be allowed. 

Bracings — There must be 22 braces in the boiler, one inch area 
at least, be nine above the flues on the front head and nine similar 
ones on the back head, none of which shall be less than 3' 6" long, 
made of good refined iron and securely riveted to the heads ; the 
other end to be extended to the shell of boiler and riveted thereto 
with two J'' rivets. Care must be exercised in the setting of 
them, so they may bear uniform tension. There must be two 
braces below flues, one on each side of manhead, and riveted to 
the heads with two |" rivets. The back end of brace to be ex- 
tended backward to side of shell and riveted thereto by means 
of two J" rivets ; and two braces in back end above flues, one 
on each side and riveted the same as the other two below 
flues. 

Manholes* — The boiler to have two manholes of the Hercules 
or Eclipse pattern, same to be of size 10"xl5", one located in 
front head, beneath the flues, and the other in rear head above 
the flues, and each to be provided with a lead gasket, grooved lid, 
two yokes and two bolts. The proportion of the whole to be 
such as will leave it as strong as any other portion of the head of 
like area. 

Steam drum* — The boiler must be provided with one steam 
drum 30" in diameter by 5' in length, shell plates of which are to 
be ^q" thick and heads i" thick, of the same quality of material 
as that in the boiler. The heads must be bumped to a radius so 
as to give as near as practicable equal strength as to that in the 
shell without bracing. The longitudinal seams of the drum are 



528 HANDBOOK ON ENGINEERING. 

to be doubly riveted with ii" diameter rivets, pitched 2J" apart 
from center to center, so as to give an efficiency of the joint of 
Tw P^^ ^®^* ^^ *^® solid jDlate. 

Manhole in drum* — The drum must be j^rovided with Her- 
cules or Eclipse Patented Manhole, same to be of size 10" x 15", 
located in the center of one head, and to be provided with a 
grooved lid, lead gasket, two yokes and two bolts. The propor- 
tion of the whole to be such as will leave it as strong as any other 
portion of the head of like area. 

To attach to boilets. — The steam drum must be attached to 
the boiler by means of two flange steel connecting legs, 8" in 
diameter by 12" in length, and securely riveted to boiler and 
steam drum shell. 

Mud drum* — Boiler must be provided with one mud drum 
24" in diameter and of sufficient length so that each end may 
come flush with the outside of the boiler walls on each side ; the 
quality and thickness of steel to be the same as that specified for 
the steam drum, and all seams to be single riveted ; said mud 
drum to be provided with one Hercules or Eclipse Patent Manhole 
in one end, and to be of size 9" x 14", supplied with a grooved 
lid, lead gasket, two yokes and two bolts. 

To attach to boiler* — The mud drum is to be attached to 
boiler by means of 8" diameter steel connecting leg, about 16" in 
length, properly riveted to boiler and mud drum shells. 

Flanges* — The boiler to have one 8" wrought steel flange riv- 
eted on top of steam drum ; one wrought steel flange 4" in diam- 
eter, about 5 feet from front end of boiler for safety valve one 
2" wrought steel flange on after end of boiler over the center of 
mud leg for suj^ply pipe — all flanges to be threaded ; 2" hole in 
mud drum for blow-off ; also 2 IJ" holes, one on top of boiler 
and one on end near bottom of boiler for water column. 

Fusible plugs* — To have two fusible plugs ; one inserted in 
shell from inside on second sheet, or about 5' from forwardeiid, 1 



HANDBOOK ON ENGINEERING. 529 

iuch above flues ; one plug inserted in top of flue, not more than 
thi'ee feet from after end. 

Trimmings^ — Furnish one 4" spring or dead weight safety 
valve, 4" diameter ; one water combination column ; provide same 
with two 11" valves for the steam and water connections between 
the boiler and column, and one i" valve for blow-pipe ; said blow- 
pipe to be connected with ashpit ; said combination barrel to be 
4'' diameter, 18'' long, and made of cast-iron. Also, furnish one 
water gauge having a J" x 15" Scotch glass tube, bodies polished 
with wood wheels and guards, rods, bodies threaded |" ; three 
gauge cocks f " register pattern, polished brass bodies ; one steam 
gauge with 10" dial ; one 2" brass feed valve with 2" check 
valve ; one 2" globe valve for blow-off from mud drum ; also one 
asbestos packed stop-cock for same, so as to insure against the 
possibilities of a leak through the blow-pipe. Water column to 
have crosses in place of ells. Crosses to have brass plugs. 

Castings, gffates, doors, etc* — The boiler must be provided 
with a heavy three-quarter fire front of neat design, having double 
firing and ashpit doors, anchor bolts for anchoring fire fronts in 
place, heavy deadplates, a full set of fire liners 9" deep for sup- 
porting firebrick on end, front and rear bearing bars ; a full set 
of ordinary grate bars 4 ft. long, soot door and frame for cleaning- 
out rear ashpit ; a full set of skeleton arch plates ; 12 heavy buck 
staves 9i' long, provided with tie rods, nuts and washers, heavy 
back stand with plate and expansion rollers ; also furnish wrought 
plates to cover mud drum. 

Fire tools* — Furnish in addition to above two sets of fire tools 
consisting of two pokers, two hoes, two slice-bars, two claws, and 
one six inch flue brush with i" pipe for handle. 

Breeching* — Boiler must have a breeching fitted to front head 
and fastened thereto by means of bolts, stays and suitable pieces 
of angle iron, bent to conform to circle of boiler. The underside 
of breeching is to run across the head between the lower flues and 



530 HANDBOOK ON ENGINEERING. 

the manhole, leaving the manhole freely exposed ; the sides of 
breeching are to be made of -^^" steel, the front and doors of i" 
steel ; said doors to be hung by means of strap hinges, provided 
with suitable fastenings so as to give free access to all flues when 
open. 

Uptake and dampen — An uptake having an area of 1221 
square inches must be fitted to top of breeching. Said uptake 
must be of convenient form for attaching to a stack 40" in diam- 
eter and provided with a close-fitting damper having a steel hand 
attachment, so that same may be operated conveniently from the 
boiler room floor. 

Smoke stack. — There is to be provided for the above boiler 
one smoke stack 40" in diameter by 90 feet in height, half of 
which is to be made of No. 8, and the other half of No. 10 best 
black sheet steel throughout, and supplied with two sets of four 
guy rods, each consisting of |" galvanized wire cable guy strand 
with turn buckles for same. 

In general* — The above-mentioned boiler must be made of 
strictly first-class material and workmanship throughout, and sub- 
jected to a hydrostatic pressure of 150 pounds to the square inch 
before leaving the works of the manufacture. 

Pamtingf boiler breechingf* — Smoke stack and boiler front, 
steam and mud drum, and all trimmings, to have two good coats 
of coal tar. 

Masonry* — Boiler to be set in good substantial masonry, of 
hard burned brick and good mortar, made of clean, sharp sand 
and fresh burned lime. Walls to be 18" thick. The outside walls 
to be laid up of selected hard burned brick, with close joints 
struck smooth and rubbed down. The sides, end and bridge 
walls, and boiler front, to have a foundation of 24" wide and 12' 
deep, laid in Portland cement. The ash pit to be paved with 
hard burned brick set on edge firmly, imbedded in Portland 
cement. For a distance of seven feet in front of the boiler and 



HANDBOOK ON ENGINEERING. 531 

continuing across entire width, of front of boiler setting to be 
paved with hard burned brick set on edge, firmly imbedded in 
sand. The walls to be carried up to the full height and a row- 
lock course of brick 4" thick to be carried over top of boiler from 
side wall to side wall, extending the whole length of boiler, and 
the entire arch to . be plastered over on the outside with mortar. 
The bridge walls to be 24", carried up to within 6" of under 
side of boiler. The top of bridge wall to be of fire brick and 
made in the form of an inverted arch, conforming to the shell of 
the boiler. The space under boiler and back of bridge wall to 
the back end of boiler, to be filled in with earth or sand and the 
top paved with brick, and tapering from bridge wall back to back 
end to 12" at back end, and in a similar form and shape, that is, 
inverted arch. The uptake for returning the smoke and heat at 
back end of boiler, to be arched over from rear wall against the 
back head of boiler 2" above the tubes, the arch being made of arch 
fire brick, and backed up with red brick. Furnace to be lined 
throughout with first quality fire brick, dipped in fire clay with 
close joints and fire brick rubbed to place, from a point 2" below 
grates, to where it safes in against boiler, and to be continued fire 
brick as far back as the rear end of setting and across rear end of 
same ; it being the intent that all interior surfaces of the setting 
with which the heat comes in contact, shall be faced with fire 
brick. Every sixth course to be a header course. 

Smoke connections, — The connection from boiler to chimney 
to be made of No. 12 black iron, with cleaning door and damper 
in same. 

BANKING FIRES. 

Different engineers pursue different methods in banking fires. 
One method is to push the fire back one-third towards the bridge 
wall, and clean off the grate in front. Then shovel in from 150 
to 300 lbs. of fine coal on top of the fire, closing ash-pit doors 



532 HANDBOOK ON ENGINEERING. 

and leaving furnace doors open, with damper open enough to let 
the gases escape. Others bank after this fashion but close all 
doors and air holes, leaving the damper partially open. Another 
method is to level the fire all over the grate, and shovel in from 
150 to 500 lbs. of fine coal, — depending on the size of the 
grate, — and then cover the whole surface with wet ashes to a 
good depth, so that no fire nor flame can be seen, then close the 
ash-pit doors, leaving the furnace doors ajar, and leave the 
damper partially open so that the gases may escape. In the 
morning, rake out the ashes, clean the fire, and throw in fresh 
coal. 

INSTRUCTIONS FOR BOILER ATTENDANTS. 

The following instructions apply more particularly to horizontal 
return tubular boilers, although in a general way they are appli- 
cable to all types of boilers. 

Never start a fire under a boiler until you are positively certain 
that there is sufficient water in the boiler, — at least two gauges 
of water. Do not trust to the water gauge alone, but try the 
gauge cocks also, and try them at intervals during the day, be- 
cause the water-gauge pipe connections may be choked and cause 
a false water level. 

Before starting a fire be sure that the blow-off cock is closed 
and not leaking. 

Before it is tim<e to start the engine, pump up three gauges of 
water, and blow off one gauge, in order to get rid of mud and 
other sediment. If the boiler has a surface blow-off, — commonly 
called a "skimmer," — blow off the scum before stopping the 
engine for the day. 

When the day's work is done, leave three gauges of water in 
the boiler, to allow for leakage and evaporation during the night. 

Never raise steam hurriedly. Sudden changes of temperature 
may produce fractures, or start leaks. 



HANDBOOK ON ENGINEEKING. 533 

In starting a fire in a furnace, a good plan is to cover the grate 
with a thin layer of coal and to place the shavings and wood on 
the coal and then light the shavings. 

The advantage of placing a covering of coal on the grate before 
the wood and shavings, is that it is a saving of fuel, as the heat 
that would be transmitted to the bars is absorbed by the coal, and 
the bars are also protected from the extreme heat of the fresh 
fire. 

Lift the safety-valve, — if of the lever pattern, — every morn- 
ing while raising steam, and satisfy yourself that it is in good 
working order, and that the pi is set at the proper point on the 
lever. The most disastrous explosions have occurred with boilers 
whose safety-valves had been stuck down or overloaded. 

Keep the boiler shell free of soot. Soot is a very good non- 
conductor of heat, and considered worse than scale inside of a 
boiler. 

Keep your boiler tubes free from soot and dust. Choked tubes 
impair the draft. The tubes should be cleaned twice a week, or 
oftener. 

Soot collects also in a stack or chimney and in the connection 
between the" breeching "and stack, and interferes with the draft. 

Open your boiler every two weeks, or, as often as necessary, — 
depending on the kind of feed-water used, — and clean out the 
mud and scale. At the same time examine all of the stays, and 
see that they are taut and in good order. Also, look for pitting 
around the mud-drum connection, and for grooving in the side 
seams. Examine all outlets and pipe connections, and look for 
indications of " bagging " in the furnace sheets. 

Clean off the fusible plugs both inside and outside of the boiler. 
A fusible plug covered with soot on the fire side, and with scale 
on the water side, is no longer a " safety plug." Renew the 
filling in safety plugs, at least once a year. They are filled with 
pure Banca tin. 



534 HANDBOOK ON ENGINEERING. 

Be perfectly satisfied that your boiler is in good condition 
internally before you close it up. 

Just as soon as you have fastened the man-head in its place, 
turn on the feed-water until you get at least three gauges of water. 
Fires have been built under emptj^ boilers, and will be again, if 
you forget to turn on the feed water after cleaning out. 

Do not empty a boiler while it is under steam pressure, but 
allow it to get cold before letting the water run out. 

If you are in a great hurry and can't wait for the boiler to cool 
down, nor for the brickwork or anything else to cool down, draw 
the fire and open the furnace and ash-pit doors, then turn on the 
feed water, and from time to time blow out, until the steam gauge 
shows no pressure ; then shut .off the feed-water, raise the safety 
valve, open the blow-off cock, then open up the boiler. 

Before opening a man -hole, lift the safety-valve, so as to be 
sure that there is neither pressure nor vacuum in the boiler. 

Look well after the brick -work surrounding your boiler, and 
stop all cracks in the walls with mortar or cement, as soon as 
discovered. They impede the draft, and cool the plates of the 
boiler, causing a waste of fuel. 

See that the bridge-wall is in perfect condition, because a gap 
in the bridge wall might cause a " bag " in the boiler by concen- 
trating the flames on one spot. 

Never allow any bare places on the grate, nor any accumulation 
of ashes, or dead coal in the corners of the furnace, as such 
places admit great quantities of cold air into the furnace, and 
render the combustion very imperfect. 

In firing with anthracite coal, do not poke and stir up the fire, 
as with soft coal, but let it alone. 

In firing soft slack coal, fire very lightly but frequently, carry- 
ing a thin fire. 

In iiting with soft lump coal, carry a thick fire, say from six 
to eight inches deep, according to the size of the furnace. 



HANDBOOK ON ENGINEERING. 535 

In firing up, you may spread the fresh coal evenly all over the 
grate, or, you may push the live coals back towards the bridge- 
wall, leaving a thin bed of live coals near the furnace doors, and 
spreading the fresh coal on top of it. This is called carrying a 
coking fire. Some prefer the one and some the other method of 
firing. 

In cas'e you should find the water in the boiler out of sight, 
and a heavy fire in the furnace, don't get rattled, and don't lose 
your head. Open the furnace doors, and close the ash-pit doors, 
and cover the fire with wet ashes, or damp clay, completely 
smothering it. Let everything else alone, including the safety 
valve and the engine. Now wait until the boiler cools down and 
the gauge shows no pressure, then turn on the feed-water. 

On the other hand, if there is but very little fire in the furnace, 
you may draw the fire, instead of covering it with ashes or clay. 

If your boiler foams badly and you are uncertain as to the 
water level, stop the engine, and the true water level will show 
itself at once. 

If your boiler primes and water is carried over to the engine, 
it shows that there is want of sufficient steam room in the boiler. 
Either put a dry-pipe in the boiler, or, increase the steam pressure 
if the boiler will safely stand it. 

Never attempt to calk a leaky seam in a boiler under steam 
pressure, because the jar caused by the hammer blows might 
cause a rupture of the seam. Better to be on the safe side 
always when repairs are required in a steam boiler, and wait until 
the boiler is cold. The above applies to steam pipes and valve 
casings, also. 

Never open any steam valves suddenly, nor close them sud- 
denly either, because it is highly dangerous to do so, particularly 
if there is considerable water in the pipes. The effect is the same 
as water hammer in water pipes. 

Smoke is caused by too little air supply, or by the flames being 



536 HANDBOOK ON ENGINEERING. 

prematurely cooled. Therefore, after firing up with fresh coal, 
it might be necessary to leave the furnace doors ajar in order to 
supply sufficient air above the fuel. 

Eemember that it takes nearly 24 cubic feet of air for the 
proper combustion of one pound of soft coal. Hard coal does 
not require so much. 

Each and every boiler in a battery should have its own inde- 
pendent safety-valve and steam gauge. 

If you are obliged to force your fire, watch your furnace sheets 
for indications of " bagging," if the water space below the lowest 
row of tubes is cramped. Water-tube boilers are less liable to - 
suffer from the effects of forced fires than shell boilers. 

With an intensely hot fire under a shell boiler, the furnace 
sheets are liable to bag, unless there is ample water space be- 
tween the shell of the boiler and the bottom row of tubes. 

The use of mineral oil to remove or prevent boiler scale, is not 
to be recommended. 

Have your feed water analyzed, and use a scale preventer 
adapted to its requirements. 

By all means endeavor to secure a steady furnace temperature, 
and a steady steam pressure, for herein lies much economy of 
fuel. Fluctuations are wasteful. 

Put a. damper in your chimney and adjust it to the needs of 
your furnace. Try to prevail on your employer to put in a shak- 
ing grate. It will enable you to carry a steady furnace temper- 
ature, and also enable you to keep the air spaces in your grate 
free and open without breaking up your fire. 

RULES AND PROBLEMS RELATING TO STEAM BOILERS. 

To find the safe working pressure : — 

U* S» Rule. — Multiply one-sixth (|^) of the lowest tensile 
strength found, stamped on any plate in the cylindrical shell, 



HANDBOOK OX ENGINEERING. 537 

by the thickness — expressed in inches or parts of an inch — of 
the thinnest plate in the same cylindrical shell, and divide by the 
radius or half diameter — also expressed in inches — and the 
result will be the pressure allowable per square inch of surface 
for single riveting ; to which add 20 per cent for double riveting, 
when all the holes have been ' ' fairly drilled ' ' and no part of 
such hole has been punched. 

A, S. of M. £♦ Rule, — First, find the tensile strength of the 
solid plate between the centers of two adjacent rivet holes. Call 
this factor A. 

Next, find the tensile strength of the solid plate between the 
centers of two adjacent rivet holes, less the diameter of one rivet 
hole. Call this factor B. 

Next, find the shearing strength of the rivets. Call this 
factor C. 

Now divide whichever is the smaller factor B or C hj A, and 
the quotient will give the strength of the joint as compared with 
the solid plate — expressed as a percentage. Then multiply the 
tensile strength of the plates by the thickneos of plates — in frac- 
tional parts of an inch -^ and multiply this product by the per- 
centage as found above, and divide this last product by the 
radius of the shell in inches, and the quotient will be the bursting 
pressure. 

Divide this quotient by the factor of safety and the result will 
give the safe working pressure. 

Example* — What is the safe working pressure for a steel 
boiler 60 inches in diameter, with side seams double riveted, 
tensile strength of plates 60,000 lbs. per sqr. in., thickness of 
plate I inch. Diameter of rivet holes a| inch, pitch of rivets 3i 
inches, shearing strength of rivets 38,000 lbs. per sqr. in., and 
factor of safety 5 ? 

Ans. By U. S. rule, 150 lbs. per sqr. in. 
By A. S. of M. E. rule, 106^ lbs. per. sqr. in. 



^38 HANDBOOK ON ENGINEERING. 

Operation by U. S. rule: — 
60,000 



: 10,000. And, 10,000 X | = 3750. 



3750 



And, -g^=125. And, 125 X. 20 =25. 

Then, 125 +25 = 150. 

Operation by A. S. of M. E. rule: — 
r = .375". 

^" = .9375". 

Then, 60,000 X 3i X .375 = 73,125 lbs., the strength of the 
solid plate between the centers of two adjacent rivet holes. CaU 
this factor A. Also, 3J == 3.25. 

Then, 3.25 — .9375 == 2.3125. 

And, 60,000 X 2.3125 X .375 r=: 52,031.25 lbs. the strength 
of the plate between two adjacent rivet holes. Call this factor B. 

Then, .9375 X -9375 X -7854 = .69029 of a square inch, the 
area of one rivet hole. There are two rows of rivets. 

Then, .69029 X 2 = 1.38058 sqr. ins. the area of two rivet 
holes combined. 

Then, 38,000 X 1.38058 = 52,462.04 lbs., the resistance of 
rivets to shearing. Call this C. Now since B is less than C, 
divide 52,031.25 by 73,125 and get as a quotient .71 +, thus 
showing the strength of the joint to be more than 71 per cent of 
the strength of the solid plates. 

,^, 60,000 X .375 X .71 .oo k iu • +v. 

Then, . ' i-^ = 532.5 lbs. per sqr. m., the 

bursting pressure. 

532 5 

And, L~ = 106.5 lbs. per sqr. in., the" safe working 

5 

pressure. 



HANDBOOK ON ENGINEERING. c539 

To find the horse power of a horizontal return tubular boiler, 
from its heating surface : — 

Rule* — Find the heating surface in square feet, of the shell 
of the boiler, measuring from one fire line to the other. Next 
find the internal heating surface of all the tubes in square feet. 
Add the two results together and divide their sum by 12, and the 
quotient will be the H. P. approximately. The heads are 
omitted. 

Example. — What is the H. P. of a horizontal return tubular 
boiler 60 inches in diameter and 20 feet long, with 44 four-inch 
tubes each 20 feet long, the distance from fire line to fire line 
being 9 feet? Ans. 86.65 H. P. 

Operation* — The internal diameter of a 4-inch tube is 3.732 
inches. 

Then, 20 X 9 := 180 square feet of heating surface in the 
shell. 

. , 3.732X3.1416 crrnr,ona .^ ^x. • . * 

And, — . — ■ = .9770376 ft., the circumference of 

12 

one tube in feet. 

And, .9770376 X 20 X 44 = 859.793 + sqr. ft., the total 
heating surface of the tubes. 

^, 180 + 859.793 „„ ^_ , 

Then, JI = 86.65 nearly. 

To find the factor of evaporation : — 

Rule* — From the total number of heat units in one pound of 
steam at the given pressure, subtract the number of heat units in 
one pound of the feed water at its given temperature, and divide 
the remainder by 965.7, which is a constant. 

Example* — A boiler evaporates 6,000 lbs. of water per hour 
from feed-water at 210 degrees into steam at 125 lbs. gauge pies- 



540 HANDBOOK ON ENGINEERING. 

Bure, what is the equivalent evaporation "from and at," and 
what is the H. P. of the boiler? 

Ans. Equiv. evap. 6276 lbs. 
H. P. 182, nearly. 

Operation* — The total number of heat units in steam at 125 
lbs. per sqr. in. gauge pressue is 1221.5361. (See steam tables 
on p. .) The number of heat units in feed-water at 210 degrees 
equals 210.874. The latent heat of steam at atmospheric pres- : 
sure, equals 965.7. | 

Then, 1221.5351 — 210.874=^:1010.6611. 

And, '- = 1.046, the factor of evaporation. 

965.7 

And, 6000 X 1.046 = 6276 the equivalent evaporation. 

Then, ^^= 181.9 H. P. 
34.5 

To find how many pounds of steam at a given absolute pressure 
will flow through an orifice of one square inch area in one seC' | 
ond : — 

Rule. — Divide the absolute pressure by the constant number 70. 

Example* — How many pounds of steam at 85 lbs. per sqr. in. 
gauge pressure, will flow through an orifice one inch in diameter, 
in one second? Ans. 1.122 lbs. 

Operation* — A hole 1 inch in diameter has an area of .7854: 
of a sqr. inch. 

And 85 + 15 ==100 lbs. absolute. 

100 X .7854 
Then, -^ =1.122. 

The weight of a cubic foot of steam at 100 lbs. per sqr. in. 

1.122 
absolute j^ressure is .2307 of a pound. Then, n^^rj = 4.86 + 

cubic feet. 



HANDBOOK ON ENGINEERING. 541 

To find the width of a reinforcing ring for a round hole in a flat 
surface, when the ring must contain as many square inches as 
were cut out of the plate, and when the ring and the plate are of 
the same thickness : — 

Rule* — Find the area of the hole in square inches and multi- 
ply it by 2. Divide this product by .7854 and extract the square 
root of the quotient for the diameter of the ring over all. Sub- 
tract the diameter of the hole from the diameter over all, and 
divide the remainder by 2 for the width of the ring. 

Example* — What should be the width of a reinforcing ring for 
a hole 10 inches in diameter, the metal cut out, and the metal in 
the ring being | in. thick? Ans. 2^^- inches. 

Operation* — 10 X 10 X .7854 = 78.54 sqr. ins. area of hole. 

And, 78.54 X 2 ^= 157.08 sqr. ins. in both hole and ring. 
157.08 

^^^' -:785r = ^^^- 

And, ^'200==U.U2-\-. 

And, 14.142 — 10 = 4.142. 

4.142 
Then, — g— ^ 2.071" or practically 2^\" . 

To find the width of a reinforcing ring for an elliptical manhole 
in a flat surface, when the ring must contain as many square 
inches as are contained in the hole, and the metal cut out and 
metal in the ring are of the same thickness : — 

Rule* — Square the short diameter of the hole and add to it six 
times the short diameter multipled by the long diameter, and to 
this product add the square of the long diameter, and extract the 
square root of the sum. From this root subtract the sum of the 
short diameter added to the long diameter, and divide the re- 
mainder by 4 for the width of the ring. 

Example* — What should be the width of a reinforcing ring 
for a manhole 11" X 15"? Ans. 



542 HANDBOOK ON ENGINEERING. 

Operation.— 11" X 11'-= 121. 

And, 11 X 15 X6=990. 

And, 15 X 15 = 225. 

Then, 121 + 990 + 225 = 1336. 

And, 71336 = 36.551. 

And, 11 + 15=26. 

Then, 36.551 — 26 = 10.551. 

10.551 

And, — g = 2.637 + ins. the width of the ring, or, prac- 
tically 2iJ ins. 

Then, 2.637X2=5.274". 

And, 11 + 5.274 r= 16.274" short diameter of ring over all. 

And, 15 + 5.274 = 20.274" long diameter over all. 

Proof: 20.274 X 16.274 X .7854= 259.13 + square inches 
area of hole and ring. 

And, 15 X 11 X .7854 = 129.59 + sqr. ins. area of hole alone. 

Then, 259.13— 129.59 = 129.54. 



THE AflOUNT OF STEAM USED WITH VALVE OPEN WIDE, 
WITH STEAH JETS AS A SMOKE PREVENTIVE. 

STEAM JETS. 

Given two boilers with separate furnaces, having 4 steam jets 
in each furnace, and each jet ^-^ inch in diameter, the steam pres- 
sure being 100 lbs. per sqr. inch by the gauge. How many 
pounds of steam at this pressure will flow through the 8 nozzles 
in 12 hours? Answer. 1739 lbs. nearly. 

Operation : tV " = -0625 ". 

Then, .0625 X -0625 X .7854 = .003067968750 sqr. inch, 
area of 1 jet. 



HANDBOOK ON ENGINEERING. 543 

And, .003067968750 X 8 = .02454375 sqr. inch, the com- 
bined area of 8 jets. 

Also, 100 + 15 == 115 lbs. per sqr. inch, the absolute steam 
pressure, 

115 
And, = 1.64 lbs. of steam per second that will flow 

70 

through an orifice of 1 square inch area. 

Then, 1.64 X .02454375 = .04025175 lbs. of steam per second 
flowing through the 8 jets. 

Again; There are 43,200 seconds in 12 hours. 
Thus: 12 X 60 X 60r--:=43,200. 

Then, .04025175 X 43,200 = 1738.8756 lbs. of steam will 
flow through 8 jets in 12 hours' time. 

Taking a high speed automatic cut-off engine using 20 lbs. of 
steam per H. P. per hour, the 8 steam jets would waste enough 
steam in 12 hours to run — 

A 10 H. P. engine for 8i hours. 
A 20 " " " 4i '* 

A 40 " " " 2| ' 

An 80 " " " IJ^ ' 

Thus^lO X 20 = 200. 

And, = 8^ nearly. 

'200 ^ ^ 

20 X 20 = 400. 

And, = 4i nearly. 

400 * -^ 



80 X 20 = 1600. 

A A 1739 , , , 

And, . = It-V nearly. 

1600 ^^ ^ 



544 



HANDBOOK ON ENGINEERING, 



THE STEAM PUMP. 



CHAPTER XIX 




The Worthington Compound Pump. 



THE WORTHINGTON COMPOUND PUMP. 

In the arrangement of steam cylinders here employed, the steam 
is used expansively, which cannot be done in the ordinary form. 
Having exerted its force through one stroke upon the smaller 
steam piston, it expands upon the larger during the return stroke, 
and operates to drive the piston in the other direction. This is, 
in effect, the same thing as using a cut-off on a crank engine, 
only with the great advantage of uniform and steady action upon 
the water. 



HANDBOOK ON ENGINEERING. 



545 



Compound cylinders are recommended in any service where 
the saving of fuel is an important consideration. In such cases, 
their greater first cost is fully justified, as they require 30 to 33 
per cent less coal than any high-pressure form on the same work. 



r^ 




The above illustration is a sectional view of the Worthington 

Compound Pump — This cut shows the steam valves 

properly set. 



On the larger sizes, a condensing apparatus is often added, thus 
securing the highest economical results. 

Any of the ordinary forms of steam pumps can be fitted with 
compound cylinders. 

It should be remembered that, as the compounds use less steam 
their boilers may be reduced materially in size and cost, compared 
with those required by the high-pressure form. This principle of 
expansion without condensation cannot be used with advantage 
where the steam pressure is below 75 lbs. 



546 



HANDBOOK ON ENGINEERING. 




The Deaiie Pump. 




The above is a sectional view of the 

DEANE DIRECT ACTING STEAM PUMP. 

The Operation of the steam valves.— In the Deaiie Steam 
Pump a rotary motion is not developed by means of which an 



HANDBOOK ON ENGINEERING. 



547 



eccentric can be made to operate the valve. It is, therefore, 
necessary to reverse the piston by an impulse derived from itself 
at the end of each stroke. This cannot be effected in an ordinary 
single-valve engine, as the valve would be moved only to the cen- 
ter of its motion, and then the whole machine would fitop. To 
overcome this difficulty, a small steam piston is provided to move 
the main valve of the engine. In the Deane Steam Pump, the 
lever 90, which is carried by the piston rod, comes in contact 




This cut shows the valves properly set. 



with the tappet when near the end of its motion, and by means 
of the valve-rod 24, moves the small slide-valve which operates 
the supplemental piston 9. The supplemental piston, carrying 
with it the main valve, is thus driven over by steam and the 
engine reversed. If, however, the supplemental piston fails 
accidentally to be moved, or to be moved with sufficient prompt- 
ness by steam, the lug on the valve-rod engages with it and 
comjjels its motion by power derived from the main engine. 



548 



HANDBOOK ON ENGINEEKING. 




SECTIONAL VIEW OF 



The Cameron" §teaiyi Pump 



The above is a sectional view of the steam end of a Cameron 
pump. 

Explanation : A is the steam cylinder ; C\ the jjistou ; i>, the 
piston rod ; L, the steam chest; F, the chest piston or plunger, 
the right-hand end of which is shown in section ; G, the slide 
valve ; JET, a starting bar connected with a handle on the outside ; 
II are reversing valves ; KK^re the bonnets over reversing valve 
chambers ; and E E are exhaust ports leading from the ends of 
steam chest direct to the main exhaust, and closed by the revers- 
ing valve II; Nis the body piece connecting the steam and water 
cylinder. 



HANDBOOK ON ENGINEERING. 549 

Operation of the Cameron Pump : Steam is admitted to the 
steam chest, and through small holes in the ends of the plunger ; 
F fills the spaces at the ends and the ports E E as far as the 
reversing valves / 1; with the plunger F and slide valve G in 
position to the right (as shown in cut), steam would be admitted 
to the right-hand end of the steam cylinder A^ and the j^iston C 
would be moved to the left. When it reaches the reversing valve 
/ it opens it and exhausts the space at the left-hand end of the 
plunger F^ through the passage E ; the expansion of steam at the 
right-hand end changes the position of the plunger F^ and with it 
the slide valve (r, and the motion of the piston C is instantly 
reversed. The operation repeated makes the motion continuous. 
In its movements, the plunger F acts as a slide valve to shut off 
the ports E E, and is cushioned on the confined steam between 
the jDorts and steam chest cover. The reversing, valves / / are 
closed immediately the piston (7 leaves them , by pressure of steam 
on their outer ends, conveyed direct from the steam chest. 

Operation. — Supposing the steam piston C moving from right 
to left: When it reaches the reversing valve / it opens it and 
exhausts the space on the left-hand end of the plunger F, through 
the passage E, which leads to the exhaust pipe ; the greater pres- 
sure inside of the steam chest changes the position of the plunger 
F and slide valve G, and the motion of the piston C is instantly 
reversed. The same operation repeated at each stroke makes the 
motion continuous. The reversing valves 7 J are closed by a pres- 
sure of steam on their large ends, conveyed by an unseen passage 
direct from the steam chest. When a pump is first connected, 
remove the bonnets K K and valves 1 1 and blow steam through 
to remove any dirt, oil or gum that may be lodged in the steam 
ports. Take valve i^, valve G and II out and wipe off with 
clean waste, and then oil and put back. Then see that the pack- 
ing is not too tight. When a Cameron pump has been run a long 
time, the plunger F becomes worn and leaks enough steam to 



550 



HANDBOOK ON ENGINEEPvING. 



cause the valve F to become balanced. The effect of this is, the 
pump will remain on the end ; to overcome this, take out plunger 
F^ or piston, as it is called by some, and drill the little hole that 
you will find in the ends of same a little larger, say about one- 
fourth larger ; that will increase the pressure on both ends of 
plunger F; as soon as the piston comes in contact with valve 1 
the steam is exhausted to exhaust pipe. 




The above is a sectional cut of 



THE KNOWLES DIRECT ACTING STEAH PUMP. 



Explanation of steam valves^ etc* — The Knowles, in fact, all 
first-class direct acting steam pumps, is absolutely free from what 
is termed a " dead center," when in first-class order. 

This feature in the Knowles Pump is secured by a very simple 
and ingenious mechanical arrangement, i. e., by the use of an 
auxiliary piston which works in the steam chest and drives the 
main valve. This auxiliary or " chest piston," as it is called, is 
driven backward and forward by the pressure of steam, carrying 



HANDBOOK ON ENGINEERING. 551 

with it the main valve, which valve, in turn, gives steam to the 
main steam piston that operates the pump. This main valve is a 
plain slide valve of the B form, working on a flat seat. The chest 
piston is slightly rotated by the valve motion ; this rotative move- 
ment places the small steam ports, D, E^ F (which are located in 




The Kuowles Direct Acting Steam Pump. 

the under side of the said chest piston) , in proper contact with 
corresponding ports A B cut in the steam chest No. 31. The 
steam entering through the port at one end and filling the space 
between the chest piston and the head, drives the said piston to 
the end of its stroke and, as before mentioned, carries the main 
slide valve with it. When the chest piston has traveled a certain 
distance, a port on the opposite end is uncovered and steam there 
enters, stopping its further travel by giving it the necessary 



552 



HANDBOOK ON ENGINEERING. 



cushion. In other words, when the rotation motion is given to 
the auxihary or valve driving piston b}^ the mechanism outside, 
it opens the port to steam admission on one end, and at the same 
time opens the port on the other end to the exhaust. 




This cut shows the valves properly- set. 



Operation of the Knowles Pump is as follows : The piston rod, 
with the tappet arm, moves backward and forward from the 
impulse given by the steam piston. At the lower part of this 
tappet arm is attached a stud or bolt, on which there is a friction 
roller. This roller coming in contact with the " rocker bar" at 
the end of each stroke, operates the latter. The motion given the 
' ' rocker bar ' ' is transmitted to the valve rod by means of the 
connection between, causing the valve rod to partially rotate. 
This action, as mentioned above, operates the chest piston, which 
carries with it the main slide valve, the said valve giving steam to 
the main piston. The operation of the pump is complete and 



HANDBOOK ON ENGINEERING. 553 

continuous. The upper end of the tappet arm does not come in 
contact with the tappets on the valve rod, unless the steam pres- 
sure from any cause, should fail to move the chest piston, in which 
case the tappet arm moves it mechanically. 

NOTICE. 

1. Should the pump run longer stroke one way than the other, 
simply lengthen or shorten the rocker connection (part 25^ so 
that rocker bar (part 23) will touch rocker roller {20) equally 
distant from center ^22). 

2. Should a pump hesitate in making its return stroke, it is be- 
cause rocker roller (^20) is too low and does not come in contact 
with the rocker bar {23) soon enough. To raise it, take out 
rocker roller stud (20 A), give the set screw in this stud a suffi- 
cient downward turn, and the stud with its roller may at once be 
raised to proper height. 

3. Should valve rod (17) ever have a tendency to tremble, 
slightly tighten up the valve rod stuffing box nut (28) . When 
the valve motion is properly adjusted, tappet tip {16) should 
not quite touch collar {15) and clamp {27). Rocker roller 
{20)^ coming in contact with rocker bar {23) will reverse the 
stroke. 

Opcf ation and construction of the 

HOOKER DIRECT=ACTINQ STEAM=PUMP. 

The parts being in position, as shown, the steam on being ad- 
mitted to the center of the valve chamber, brings its pressure to 
bear on the main and supplemental flat slide valve 4 and 7, and 
also within the recess in the center of the supplemental piston 6. 
The recess incloses the main valve 4, so that this valve will move 
with the supplemental piston whenever the steam is supplied to 



554 



HANDBOOK ON ENGINEEKING. 



and exhausted from each end of this piston. The live steam 
passes through the left-hand ports A^ B^, driving the main piston 
2 to the right, and the exhaust j^asses out through the right-hand 
ports A and C under the cavity in the main valve 4 to the atmos- 
phere. As the main piston nears the right hand port, the valve 
lever i5, which is attached to the piston rod 3, brings the dog i 7, 
in plate i6, in contact with the valve arm 15, and moves the sup- 
plemental valve 7 to the right, thus supplying live steam to the 




right of the supplemental piston 6', and exhausting from the left 
through the ports e e. As the supplemental piston incloses the 
main valve, this valve is carried with it to the left. Steam now 
enters the right-hand ports ^1 B and is exhausted from the left- 
hand main port A. The engine commences its return stroke and 
the operation just described becomes continuous. As the main 
piston (2) closes the main port (^) to the right, it is arrested on 
compressed exhaust steam. The main valve 4 having closed the 
auxihary ports (B) leading to that end of the main cylinder, the 



HAJNDBOOK ON ENGINEERING. 



555 




iThis cut shows the steam valves properly set. 

steam being supplied through both the main and auxiliary ports, 
but released through the main ports only. 



BLAKE STEAM PUflP. 

Description of the Blake Steam Pump* — The Blake Steam 
Pump is absolutely positive in its action ; that is to say, the 
operation at the slowest speed under any pressure, is perfectly 
continuous, and the pump is never liable to stop as the main valve 
passes its center, if the pump is in good order. An ingenious and 
simple arrangement is used in the Blake Pump to overcome the 
" dead center," as will be seen from the engravings. 

Operation of the Blake Steam Pump, — The main or pump 
driving piston A could not be made to work slowly were the 
main valve to derive its movement soJely from this piston ; for 



556 



HANDBOOK ON ENGINEERING. 



wlieu this valve had reached the center of its stroke, in which 
position the ports leading to the main cylinder would be closed, 




The Blake Steam Pump. 

no steam could enter the cylinder to act on said piston, con- 
sequently, the latter would come to rest, since its momentum 
would be insufficient to keep it in motion, and the main 
valve would remain in its central position or " dead cen- 
ter." To shift this valve from its central position and 
admit steam in front of the main piston (whereby the motion 
of the piston is reversed and its action continued), some agent 
independent of the main piston must be used. In the Blake 
Pump, this independent agent is the supplemental or valve-driving 
piston B. The main valve, which controls the admission of steam 
to, and the escape of steam from, the main cylinder, is divided 
into two parts, one of which, (7, slides upon a seat on the main 
cylinder, and, at the same time, affords a seat for the other part, 



HANDBOOK ON ENGINEERING. 



557 



i>, which sUdes upon the upper face of C. As shown in the en- 
graving, D is at the left-hand end of its stroke, and C at the 
opposite, or right-hand end of its stroke. Steam from the steam- 
chest »/ is, therefore, entering the right-hand end of the main 
cylinder through the ports E and H, and the exhaust is escap- 
ing through the ports H^ and ^i, K and 3f, which causes the 




Sectional views of steam cylinder, valves, etc., 
,of the' Blake Steam Pump. 



main j^iston A to move from right to left. When this i3iston has 
nearly reached the left-hand end of its cylinder the valve motion 



558 



HANDBOOK ON ENGINEERING. 



(not shown) moves the valve-rod P, and this causes (7, together 
with its supplemental valve R and S S^ (which form, with (7, one 
casting) to be moved from right to left. This movement causes 
steam to be admitted to the left-hand end of the supplemental 
cylinder, whereby its piston B will be forced toward the right, 
carrying D with it to the opposite or right-hand end of its stroke ; 
for the movement of S closes N (the steam port leading to the 




This cut shows the valves properly set. 



right-hand end), and the movement of 8^ opens N'^ (the port 
leading to the opposite, or left-hand end). At the same time the 
movement of opens the right-hand end of the cylinder to 
the exhaust through the exhaust ports X and Z. The ports C 
and D now have positions opposite to those shown in the engrav- 
ings, and steam is, therefore, entering the main cylinder through 
the jDorts E^ and i?^, and escaping through the ports H^ E, K 
and i>/, which will cause the main piston A to move in the op- 



HANDBOOK ON ENGINEERING. 559 

posite direction, or from left to right, and operations similar to 
those alread}' described will follow, when the piston approaches 
the right-hand end of its cylinder. By this simple arrangement 
the pump is rendered positive in its action ; that is, it will in- 
stantly start and continue working the moment steam is admitted 
to the steam chest. The main piston A cannot strike the head of 
the cylinder, for the main valve has a head ; or, in other words, 
steam is always admitted in front of said piston just before it 
reaches either end of its cylinder, even should the supplemental 
piston B be tardy in its action and remain with D at that end, 
toward which the piston A is moving ; for C would be moved far 
enough to open the steam port leading to the main cylinder, since 
the possible travel of C is greater than that of D. The supple- 
mental piston B cannot strike the heads of its cylinders, for in its 
alternate passage beyond the exhaust ports X and X, it cushions 
on the vapor intrapped in the ends of this cylinder. 

MISCELLANEOUS PUHP QUESTIONS. 

Q. What is a pump? A. It is hard to get a definition that 
will cover the whole ground. A pump may be said to be a 
mechanical contrivance for raising or transferring fluids ; and as a 
general thing consists of a moving piece working in a cylinder or 
other cavity ; the device having valves for admitting or retaining 
the fluids. 

Q. What two classes of ojjerations are included in the term 
"raising" fluids? A. They may be raised by drafting or suc- 
tion, from their level to that of the pump ; they may be raised 
from the level of the pump to a higher level. 

Q. Do pumps always "raise" by either method, from one 
level to a higher one, the liquid which they transfer? A. No ; in 
many cases the liquid flows by gravity to the pump ; and in some 
it is delivered at a lower level than that at which it is received. 



560 HANDBOOK ON ENGINEERING. 

Q. Where a pump is not used for raising a liquid to a higher 
level, for what is it generally used ? A. To increase or decrease 
its jDressure. 

Q. What classes of liquids are handled by pumps ? A. Air, 
ammonia, lighting gas, oxygen, etc. 

Q. Name some liquids which are handled by pumps? A. 
Water, brine, beer, tan liquor, molasses, acids and oils. 

Q. Where it is not specified whether a pump is for gas or for 
liquid, which is generally understood? A. Liquid. 

Q. What gas is most frequently pumped? A. Air. 

Q. What liquid is generally understood if none other is speci- 
fied for a pump ? A. Water. 

Q, Can pumps handle hot and cold liquids? A. Yes ; though 
cold are easier handled than hot. 

Q. What is the difference between a fluid and a liquid? A. 
Every liquid is a fluid ; every fluid is not a liquid. Air is a fluid ; 
water is both a fluid and a liquid. Every liquid can be poured 
from one vessel to another. 

SUCTION. 

Q. What causes the water to rise in a pump by so-called 
suction? A. The unbalanced pressure of the air upon the surface 
of the liquid below the pump, forces the water up into the suction 
pipe when the piston is withdrawn from the liquid. 

Q. How much is the pressure of the atmosphere? A. At the 
sea level about 14.7 lbs. per square inch, or 2116.8 lbs. per square 
foot. 

Q. In what direction is this pressure exerted? A. In every 
direction equally. 

Q. What tends to prevent the water from being lifted? A. 
The force of gravity, which is the result of the attraction of the 
earth's center. 



HANDBOOK ON ENGINEERING. 561 

Q. In what direction does the force of gravity act? A. In 
radial lines towards the center of the earth. 

Q. With what force does this gravity act? A. That depends 
upon the substance upon which it is acting. 

Q. Why do you refer to the level of the sea in speaking of the 
pressure of the air and the weight of water? A. Because the air 
pressure becomes less as, in rising above the sea level, we recede 
from the center of the earth, and the weight of a given quantity 
of water or any other substance becomes less than it is at the level 
of the sea, as we approach to or recede from the center of the 
earth. 

Q. How is it that the weight of any substance becomes less if 
you go either above or below the sea level? A. The farther you 
go from the earth, the less, its attraction and the less a given 
body will weigh upon a spring balance. The farther down into 
the earth you go, the nearer you get to the center of the earth, at 
which, there being attraction upon all sides, any body would 
weigh nothing. Going from the surface of the earth towards its 
center, then, a body weighs less and less upon a spring balance. 

Q. Why do you specify a spring balance? A. Because in 
weighing by counterpoise, both the body to be weighed and the 
counterpoise by which it is weighed, would change their weights 
in the same proportion, as the position with regard to the center 
of the earth was changed. 

Q. What are the causes which principally prevent pumps from 
lifting up to the normal maximum? A. Friction ; leakage of air 
into the suction, chokes in the suction pipe. 

Q. Can a liquid be "drafted" without the expenditure of 
work ? A. No ; in drafting a liquid to the full height to which it 
can be drafted, at least as much power must be expended as 
would lift the same weight of liquid tha^ height by any mechan- 
ical means ; only the amounts of friction being different. 

Q. Then what advantage is there in having a pump draft its 



562 HANDBOOK ON ENGINEERING. 

water to the full possible height, over having it force the water 
the full height? A. Convenience in having the pump higher up. 

Q. Can a pump throw water higher or farther, with a given 
expenditure of power, where it flows in, than where it must draft 
its water? A. Yes; on the same principle that it can throw 
farther or force harder when the water is forced to its suction 
side than where it merely flows in. 

Q. What is the use of the suction chamber? A. To enable 
the pump barrel to fill where the speed is high ; to prevent 
pounding, when the pump reverses. 

Q. Upon what does the lifting capacity of a pump depend? 
A. When the pump is in good order its lifting capacity depends 
mainly upon the proportion of clearance in the cylinder and valve 
chamber to the displacement of the piston and plunger. 

Q. Which will lift further, an ordinary piston pattern pump or 
a plunger pump ? And why? A. Other things being as nearly 
equal as they can be made between these two pumps, the piston 
pump will lift the farther of the two, because the plunger pump 
has the most clearance. 

Q. What is the advantage of the suction chamber? A. To 
assist the pump in drafting, especially at high speed. 

Q. What is the advantage of the air chamber? A, To make 
the stream steady. 

Q. What difficulty is sometimes met with in using an air 
chamber? A. Where the pressure is very great sometimes the 
air is absorbed by the water, and thus the cushion is detroyed. 

FORCING. 

Q. What will be the volume of the air in the air chamber of a 
force pump, when the pump is forcing against a head of 67.6 
feet? A. It will be reduced to half its ordinary volume, because 
it will be at the pressure of two atmospheres. 



HANDBOOK ON ENGINEERING. 



563 




The above cut shows a pump with a- removable cylinder 
or liner, and is packed with fibrous packing set out by adjustable 
set screws and nuts. This style of a pump is the best for small 
water-works or elevators, or where a pump is used where the 
water is muddy or sandy. 

To find the horse power necessary to elevate water to a 
given height : Multiply the total weight of the water in pounds 
by the height in feet and divide the product by 33,000 (an allow- 
ance of 25 per cent should be added for water friction, and a further 
allowance of 25 per cent for loss in steam cylinder.) 

The heights to which pumps will force water when running at 



564 HANDBOOK ON ENGINEERING. 

100 feet piston speed per minute, and the suction and discharge 
pipes being of moderate length, will be found by dividing the area 
of the steam piston by the area of the water piston, and multi- 
plying the quotient by the steam pressure. Deduct 40 per cent 
for friction and divide the remainder by .434. 

Example^ — To what height will an 8-inch steam piston, with 
a 5 -inch water piston, force water, the steam pressure being 80 
lbs. by gauge? Ans. 283 ft. nearly. 

Operation. — Area of steam piston = 50.26 sq. ins. 
" " water " =19.63 " " 

50 26 
Then, ~—l = 2.56. And 2.56 X 80 = 204.80 lbs. 
' 19.63 

Then, 204.80 less 40% = 122.88 lbs. 

, , 122.88 ^ . ^ 

And, = 283 -f feet. 

An allowance must be made where long pipes are used. 

The normal speed of pumps is taken at 100 piston feet per 
minute, which speed can be considerably increased if desired. 

For feeding boilers, a speed of 25 to 50 piston feet per minute 
is most desirable. 

A gallon of water, U.S. Standard, weighs S^ lbs. and contains 
231 cubic inches. 

A cubic foot of water weighs 62.425 lbs. and contains 1,728 
cubic inches, or 7 J gallons. 

Doubling the diameter of a pipe increases its capacity four 
times. 

Friction of liquids in pipes increases as the square of the 
velocity. 

To find the area of a piston, square the diameter and multiply 
by .7854. 



HANDBOOK ON ENGINEERING. 565 

Boilers requii'e, for each nominal horse-power, about one cubic 
foot of feed water per hour. 

In calculating horse power of tubular or flue boilers, consider 
15 square feet of heating surface equivalent to one nominal horse- 
power. 

To find the pressure in pounds per square inch of a column 
of water, multiply the height of a column in feet by .434. 
Approximately, we say that every foot of elevation is equal to 
one-half lb. pressure per square inch; this allows for ordinary 
friction. 

The area of the steam piston, multiplied by the steam pressure, 
gives the total amount of pressure that can be exerted. The 
area of the water piston, multiplied by the pressure of water per 
square inch, gives the resistance. A margin must be made 
between the power and the resistance to move the pistons at the 
required speed — say from 20 to 40 per cent, according to speed 
and other conditions. 

To find the capacity of a cylinder in gallons : Multiplying the 
area in inches by the length of stroke in inches will give the total 
number of cubic inches ; divide this amount by 231 (which is the 
cubical contents of a gallon of water) and quotient is the capacity 
in gallons. 

To find quantity of water elevated in one minute running at 100 
feet of piston speed per minute : Square the diameter of water 
cylinder in inches and multiply by 4. 

Example: Capacity of a five-inch cylinder is desired.* The 
square of the diameter (5 inches) is 25, which, multiplied by 4, 
gives 100, which is gallons per minute, approximately. 

Q. " What is the reason that a steam pump of the horizontal 
double acting type should throw an intermitting stream under 
pressure, like the stream from milking a cow, only not quite so 
bad as that? I have tried valves of different sizes, with different 
amount of rise, springs or valves of different tension, different 



566 HANDBOOK ON ENGINEERING. 

kinds of packing in water j^iston, and different sized water ports 
or passages, without any apparent difference." A. Steam pumps 
of the horizontal double-acting type are not alone in throwing an 
intermitting stream. The same thing shows up in vertical single- 
acting pumps ; and all horizontal double-acting pumps do not so 
behave. The steam fire engine shows that no type of pump is 
exempt from •' squirting." 

Q. How may this squirting be lessened? A. By increasing 
the suction valve area ; by giving more suction chamber and 
more air chamber. 
********* 

Q. What is a sinking pump? A. One which can be raised and 
lowered conveniently, for pumj)ing out drowned mines, etc. 

Q. Into what main general classes may reciprocating cylinder 
pumps be divided ? A. Into single acting and double acting. 

Q. What is a single acting reciprocating pump ? A. One in 
which each reciprocation or single stroke in one direction causes 
one influx of fluid, and each reciprocation or single stroke in the 
opposite direction causes one discharge of fluid. In other words, 
the pump, as regards its action, is single ended. 

Q. What is a double acting reciprocating pump ? A. One in 
which each end acts alternately for suction and discharge. Re- 
ciprocation of the piston in one direction causes an influx of 
fluid into one end of the pump from the source, and a discharge 
of fluid at the opposite end ; on the return stroke the former 
suction end becomes the discharge end. In other words, the 
pump is double ended in its action ; or is " double-acting." 

Q. What is the special advantage of having double-acting 
pump cylinders? A. The column of water is kept in motion 
more constantly, and hence there is less jar ; smaller pipes may 

be used. 

********* ^ j^ 

Q. How may those pumps which are driven by steam against a 



HANDBOOK ON ENGINEERING. 567 

steam piston be divided ? A. Into those which have a fly wheel 
and those which have no fly wheel. 

Q. Into what classes may those pumps which are driven by 
steam, without a fly wheel, be divided? A. Into direct acting 
and duplex. 

Q. What is the advantage of a fly wheel steam pump? A. 
Steadiness of action ; the capability of using the steam expan- 
sively. 

Q. What are the disadvantages of fly wheel pumps? A. Great 
weight ; inability to run them very slowly without gearing down 
from the fly wheel shaft, as the wheel must run comparatively 
rapidly. 

Q. What is a direct-acting steam pump? A. One in which 
there is no rotary motion, the piston being reversed by an impulse 
derived from itself at or near the end of each stroke. There is 
but one steam cylinder for one water cylinder ; the valve motion 
of the steam cylinder being controlled by the action of the steam 
in that cylinder. 

HOW TO SET THE STEAH VALVES ON A DUPLEX PUMP. 

The steam valves on Duplex pumps generally have no outside 
lap, consequently, when in its central position, it just covers the 
steam ports leading to the opposite ends of cylinder. 

By lost motion is meant, the distance a valve-rod travels 
before moving the valve; if the steam-chest cover is off the 
amount of lost motion is shown by the distance the valve can be 
moved back and forth before coming in contact with the valve- 
rod nut. The object of lost motion is to allow one pump to 
almost complete its stroke before moving the valve of its fellow 
engine. As the steam piston is nearing the end of its stroke, it 
moves the valve of its fellow engine, admitting steam and start- 
ing its fellow engine as it lays down its own work ; in other words, 



568 



HANDBOOK ON ENGINEERING. 



the other picks it up. The amount of lost motion required is 
enough to allow each piston to complete its stroke ; in other words, 
if there was no lost motion, as each piston would pass the 
center of their travel, they would move the valve of their 
fellow engine, and the result would be a very short stroke. 




This cut shows the steam valves properly set. 



To set the steam valves, move the steam piston towards the 
steam cylinder head until it comes in contact with the head ;,mark 
with a scribe on the piston-rod at the face of the stuffing-box 
follower on steam end ; then move the piston to its contact stroke 
on the opposite end and make another mark on the piston-rod, 
exactly half way between the face of the stuffing-box follower on 
the steam end, and the first mark. Then move the piston back 
until the middle mark is at the face of piston-rod stuffing-box 
follower on the pump end. This operation brings the piston 
exactly in the middle of the stroke. Then take off the steam 



HANDBOOK ON ENGINEERING. e569 

chest cover, place the slide-valve in the center, exactly over the 
steam ports. Place the slide-valve nut in exact center between 
the jaws of the slide-valve, screw the valve-rod through the nut 
until the eye on the valve-rod head comes in line with the eye of 
the valve-rod link ; slip the valve-rod head pin through head and 
the valve is set. Repeat the same operation on the other side of 
the pump. Where a pump is fitted with four hexagon valve-rod 
nuts, two either end of the slide-valve, instead of one nut in the 
center of the valve, set and lock these hexagon nuts at equal dis- 
tances from the outer end of the slide-valve jaws, allowing a little 
lost motion, varying from i" on high-pressure pumps, to, say, 
i" on low service pumps, on each side of valve ; if the steam 
piston hits the head, take up some of your lost motion ; if the 
steam piston should not make a full stroke, give more lost motion. 

THE BEST MANNER OF ARRANGING PIPE CONNECTIONS. 

For the purpose of showing good arrangement, the above cut 
is presented. 

On lon^ lifts it is necessary to provide the suction pipe S 
with a foot-valve F. By the use of a foot-valve, the pipe and 
cylinders are constantly kept charged with water, allowing the 
pump to start without having to free itself and the suction pipe 
of air. In case of a long lift, the vacuum chamber V is also 
essential. This may be readily constructed by using a tee in place 
of the elbow E, extending the suction pipe and placing a cap 
upon the top. In order to keep the water back when the pump is 
being examined or repaired, a gate valve should be placed in the 
delivery pipe. It sometimes happens that, either purposely or 
through a leak in the foot-vaive, the suction chamber becomes 
empty. For the purpose of charging the suction pipe and cylin- 
der a " charging pipe " P is placed outside the check valve, 
connecting the delivery pipe D with the suction. In order that 



570 



HANDBOOK ON ENGTNEEETNO . 



the pump, in starting, may free itself of air, a check valve 6^ and 
a " starting i3ipe " A should be provided. This pipe may be 



r^ 




ARRANGEMENT OF PIPE CONNECTIONS. 



led to any convenient place of discharge. After the pump has 
started, the valve in the starting pipe should be closed gradually. 
Faulty connections are generally the cause of the improper action 



HANDBOOK ON ENGINEERING. 571 

of a pumi3. Great care should, therefore, be taken to have 
everything right before starting. A very small leak in the suc- 
tion will cause a pump to work badly. 

Q. What is the peculiarity of the duplex type? A. There are 
two steam cjdinders and two water cylinders ; the piston of one of 
these cylinders works the valve of the other cylinder, and vice versa. 
Neither half can work alone. This name is entirely arbitrary. 

Q. How would you call a pumping machine in which there are 
two steam cylinders, each operating a water cylinder in line with 
it ; each half being a perfect pumping machine independent of the 
other side? A. A " double " pump. 

Q. Can a direct acting steam pump use steam expansively? 
A. Not to any extent ; in fact, there would be danger of sticking 
upon the centers in most cases, if there was lap and expansion. 

Q. What is the reason that a single cylinder engine cannot well 
reverse itself without a fly wheel, by means of the ordinary single 
D valve? A. Because when the valve was at mid-travel, both 
ports of the valve seat would be closed by the valva faces, and 
neither exhaust nor admission take place. 

Q. What means are employed in a direct acting steam pump to 
move the valve? A. A small supplementary piston is used; this 
supplementary piston being actuated by the main piston in any 
one of several different ways. 

Q. What are the principal ways of working the supplementary 
piston from the main piston? A. (1) The main piston strikes 
the tappet of a small valve, which opens an exhaust passage in 
one end of the cylinder, containing a supplementary piston, and 
having live steam pressing upon both ends of the supplementary 
piston ; (2) by the main piston striking a rod passing through 
the cylinder head, and moving a lever which controls the motion 
of the part of the main valve to which is attached the valves which 
moves the supplementary piston ; (3) the main piston rod carries 
a tappet arm, which twists the stem of the supplementary piston, 



572 HANDBOOK ON ENGINEERING. 

thus uucoveriiig ports which cause its motion ; (4) a projection 
upon the main piston rod engages the stem and operates the valve 
which moves the supplementary piston, but if that valve should 
not, by means of its steam passages, cause quick enough or sure 
enough motion of the supplementary piston, a lug upon this stem 
moves the supplementary piston. 

Q. In the first of these four classes, what is the principal 
element in the valve motion? A. A difference in area between 
the eduction port of the supplemental piston and its induction port 

Q. What is the principal feature in the second class? A. A 
regular slide valve letting steam upon alternate ends of the sup- 
plemental jjiston. 

Q. In the third class, what is the main feature? A. A twist- 
ing motion in the supplemental piston. 

Q. In the fourth class, what is the principal feature? A. 
Movement of the supplemental piston by steam controlled by a 
slide valve, and by the mechanical action of the slide valve itself 
if its steam distribution is defective. 

Q. What are the objections to most pumps of the direct acting 
type? A. The unbalanced condition of the auxiliary pistons in 
the exhaust side, causing a loss of steam when the parts are worn, 
the choking up of the small ports for the auxiliary pistons, by the 
gumming and caking of the oil therein. 

Q. Can the ordinary direct acting steam pump use steam 
expansively? A. No. 

Q. How may this be done? A. By compounding. 

Q. What is to be taken into consideration in the use of com- 
pound steam pumps? A. That they are designed for a certain 
range of pressure — say from 80 to 120 pounds boiler pressure, 
and will do their best work between these pressures. 

Q. Have all direct-acting steam pumps intermittent valve 
motion? A. No; there are some which have continuous valve 
motion. 



HANDBOOK ON ENGINEERING. 573 

Q. In most direct-acting steam pumps, are the auxiliary piston 
heads made together or in separate pieces? A. Together. 

Q. They are in contact with the steam in the chest? A. Yes. 

Q. What should be said about the location of a pump? A. It 
should be as near the source of supply as is convenient. 

Q. What may be said about convenience in repairs? A. The 
pump should have room left upon all sides ; and upon both ends 
equal to its length, for the removal of the piston rods in case of 
repairs. 

Q. If the floor is not strong enough, how may a good founda- 
tion be made ? A. By digging two or three feet into the ground 
and building up the proper height with stone or brick laid in 
strong cement, with a cap stone. 

Q. What may be said about suction j^ipes? A. They must be 
as large as possible ; the longer they are the greater in diameter 
they should be ; they should be as straight as possible, and as 
free from bends and valves ; they must be air-tight ; they must 
not be allowed to get obstructed by foreign substances. 

Q. What may be said about the area of strainer holes? A. 
They should have an aggregate area about five times that of the 
suction pipe. 

Q. Where are foot valves necessary ? A. Upon long suctions 
or high lifts. 

Q. Should two pumps take their suction from one pipe ? A. It 
should be avoided, unless the pipe is very large ; and in case both 
suctions should be arranged so that one of the pumps should not 
have to draft at right-angles to the flow of water going to the other 
pump. 

Q. What arrangement should be made where it is necessary to 
have two pumps draft from one suction? A. There should be a 
Y connection. 

Q. What is a good way to reduce the friction in suction pipes 
where there are many bends? A. To use bends of wrought- 



574 HANDBOOK ON ENGINEERING. 

iron pipe of as long a radius as possible, instead of oast-iron 
elbows. 

Q. What may be said about the lower end of the suction pipe? 
A. It should generally have a strainer ; and if the lift is over 12 
to 15 feet, should have a foot valve. 

Q. What is a good thing to do with the discharge pipe near 
the pump? A. To put a valve in it near the pump, to keep 
the water in the pipe when the water end is to be opened for 
inspection or repairs. 

Q. What provision should be made for priming the pump? A. 
There should be a pipe with a stop valve in it connected from the 
discharge pipe beyond this check valve, or from some other source 
of supi^ly, to the suction pipe, for the purpose of priming the 
pump. 

Q. When the pump is in position for piping, what care should 
be taken? A. That the pipes are of proper length, so as not to 
bring any undue strain upon them in connecting them to the pump 
as in that case they wiU be liable to give trouble by breaking or 
working the joints loose and leaking. 

Q. Does any pipe have an effective diameter as great as its 
nominal diameter? A. No; because the sides retard the flow of 
the liquid ; there is a neutral film of liquid which practically does 
not move. 

Q. Upon what does the thickness of this film of liquid depend? 
A. Upon the viscosity (commonly miscalled the "thickness") 
of the liquid ; upon the roughness, material and diameter of the 
pipe ; the pressure, etc. 

Q. When long lines of pipe are used, should the diameter of the 
pipe be the same all the way along, or should there by sections 
be decreasing diameter, as the distance from the pump increases ? 
A. Most emphatically, the pipe diameter should remain constant 
clear out to the end. 



HANDBOOK ON ENGINEERING. 575 

TAKING CARE OF A PUMP. 

Q. What can be said about taking care of a pump? A. In 
places where an inferior grade of labor is employed, oil and dirt 
are sometimes found covering the steam chest and pump to the 
depth of an inch in thickness ; stuffing boxes are allowed to go 
leaky and get loose ; the valve motion is never looked after ; lost 
motion is never taken up, and the pump will be let run in a slip- 
shod way for months, until some accident occurs. This will 
sometimes exist in places where the engine is well taken care of. 

Q. Should not as good care be taken of a steam pump as of 
an engine? A. Yes. It is a steam engine, and the fact that it 
has generally but little adjustability, should not render it liable to 
lack of care. 

Q. What is a very common thing for pump runners to do when 
anything happens? A. To condemn the pump at once without 
finding out the cause of the trouble. 

Q. What is one reason of this? A. The man who understands 
an ordinary engine, will often become quite perplexed when he 
examines the steam end of a direct acting steam pump, because 
he does not comprehend the principal feature of its construc- 
tion — that all direct acting steam pumps which have no fly 
wheels and cranks, must generally have an auxiliary piston in 
order to carry them over the " dead center." A direct acting 
steam pump is really a double engine ; a plain, flat slide valve 
admitting steam to a small piston, which in turn operates the 
main valve, which gives steam by the usual arrangement to the 
main piston. 

Q. What would save firemen and engineers much trouble with 
steam pumps? A. If they would take the trouble to examine 
their pumps carefully, and find out the way their valves were 
arranged and actuated. 

Q. Upon what does the successful perfoi'mance of a pump 



576 HANDBOOK ON ENGINEERING. 

depend, in great measure? A. Upon its proper selection from 
among the many patterns differing from each other in size, pro- 
portion and general arrangement. 

Q. What may be said about the selection of pumps? A. 
Pumps are often selected improperly for their work. As an illus- 
tration, a man who wishes to use a circulating pump for a surface 
condenser, where the water pressure upon the pump cylinder will 
never exceed 5 to 10 pounds, will buy a pump intended for boiler 
feed work, and having its steam cylinder about three times the 
area of its pump cylinder. 

Q. What will be the result in such a case? A. There will be 
little or no pressure in the steam cylinder when working on the 
condenser ; and while there is pressure sufficient to move the 
main piston, there is not enough to operate the auxiliary piston 
with positiveness. 

Q. In ordering a pump, or in asking estimates, what informa- 
tion should be given? A. In ordering a pump, it is to the inter- 
est of the i^urchaser to fully inform the maker or seller on the 
following questions : 1st. For what purpose is the pump to be 
used? What is the average steam pressure? 2d. What is- the 
liquid to be pumped ; and is it hot or cold, clear or gritty, fresh, 
salt, alkaline or acidulous? 3d. What is the maximum quantity 
to be pumped per minute or hour? 4th. To what height is the 
liquid to be lifted by suction, and what is the length of the suction 
pipe, and the number of elbows or bends? 5th. To what height 
is the liquid to be pumped, and what is the length of discharga 
pipe? 

Q. How can an engineer familiarize himself with the direction 
of the auxiliary steam and exhaust passages? A. By means of 
a piece of wire. 

Q. What is the special thing to look after in duplex pumps? 
A. That all packings are adjusted uniformly on both sides. 

Q. What would be the result of having the packings different 



HANDBOOK ON ENGINEERING. 577 

upon the two sides of a duplex pump? A. The machinery would 
run unsteadily. 

Q. If a pump works badly, what should be about the first thing 
to look at? A. The connections. 

Q. When a pump is first connected, what should be done? 
A. It should be blown through to remove dirt ; if it be of the 
class which will. permit of removing the bonnets and blowing 
through, that should be done. 

Q. What pump piston speed is recommended for continuous 
boiler feeding service? A. About 50 feet per minute. 

Q. What may be said about the care and use of steam pumps 
of all kinds ? A. It is important that the pump be properly and 
thoroughly lubricated ; that all stuffing-box, piston and plunger 
packings be nicely adjusted ; not so tight as to cause undue fric- 
tion ; nor so slack as to leak badly. 

Q. In which end of a steam-pumping machine is there most 
likely to be trouble ? A. In the water end. 

Q. If a pump slams and hammers in its water end, is it neces- 
sarily defective in its water cylinder? A. No; it may be that 
there is no suction chamber, or not enough ; or sometimes it slams 
because the suction pipe is not large enough. 

Q. What are very common defects in cheap grades of pumps? 
A. Too little valve area in the pump end ; too great lift for the 
valves. 

Q. What are the principal causes of pumps refusing to lift 
water from the source of supply? A. Among these may be 
mentioned leaky suction pipes, worn out pistons, plungers, pack- 
ings or water valves ; rotten gaskets on joints in piping or pump ; 
and sometimes a failure to jDroperly prime the pump as well as 
the suction pipe. 

Q. What is one great cause of a pump refusing to lift water 
when first started? A. It often happens that a pump refuses to 
lift water while the full pressure against which it is expected to 



578 HANDBOOK ON ENGINEERING. 

work itt resting upon the discharge valves, for the reason that the 
air within the pump chamber is not dislodged, but only compressed, 
by the motion of the plunger. It is well, therefore, to arrange 
for running without pressure until the air is expelled and water 
follows ; this is done by placing a valve in the delivery pipe 
and providing a waste delivery, to be closed after the pump has 
caught water. 

Q. Sometimes when starting, the water may not come for a 
long time ; what is the best thing to do in this case? A. First, 
oj)en the little air cock, which is generally located in the top of 
the pump, between the discharge valves and the air chamber, to 
let off any accumulation of air which may there be confined 
under pressure. Very often, by relieving the pump of this air 
pressure, it will pick up its water by suction and operate 
promptly. 

Q. What precaution must be taken in priming the pump? A. 
The air cock, which should be provided at the top of the pum23, 
should be opened to allow the escape of the air from the suction 
pipe and from the pump, and then the valve in the priming pipe 
should be opened. The pump should then be started slowly, as 
it aids in more completely filling the pump cylinders, which 
otherwise, might not occur and the pump might fail to lift water. 

Q. Is there any advantage in having air in the suction? A. 
Sometimes a small amount of air let into the suction will cause less 
jarring when the duty is very heavy. 

Q. What may be said about pumping hot water? A. Where 
the hot water is very hot, it should gravitate to the pump, instead 
of an attempt being made to draft it. 

Q. In the plunger pumps, what is about the only wearing part 
of the water end? A. The packing of the plunger stuffing-boxes. 

Q. How can a pump be prevented from freezing? A. By 
having draining cocks and opening them when the pump is 
idle. 



HANDBOOK ON ENGINEERING. 579 

Q. What may be said about leather piston packing for water 
cylinders? A. For cold water, or sandy, gritty water, the 
leather packing has many points to commend it ; it makes a 
tight piston, and one that is the least destructive to pump 
cylinders. 

Q. What is the best way to handle the square packing mostly 
employed, which is composed of alternate layers of cotton and 
rubber? A. Cut the lengths a trifle short, then there will be 
room for the packing to swell and not cause too much friction. I 
have known pistons where this precaution has not been taken to 
be fastened so securely in the cylinder by the swelling of the dry 
packing, that full steam pressure could not move them. 

Q. What is the remedy in such a case? A. Remove the 
follower, take out the different layers of packing and shorten their 
lengths. 

Q. What is the reason that some soft waters corrode pipes so 
often? A. Because they contain a large proportion of oxygen. 

Q. Will a pump with a 6" water cylinder and a 6" steam cylin- 
der force water into a boiler, the discharge from water cylinder 
being 4" diameter; boiler pressure, 80 lbs.? A. A pump with a 
6" water cylinder and 6" steam cylinder will not force water into 
the boiler which supplies it, no matter what the steam pressure, 
nor w^hat the size of discharge pipe. It will not move. The 
pressures would be equalized and there would be nothing to over- 
come friction of steam and water in pipes and cylinder. The 
foregoing case supposes that the water is to be lifted to the pump ; 
or at least that there shall be no head ; also, that there shall be 
no fall from pump to boiler. If there were sufficient head or fall 
to overcome all the various frictions, and no lift, the pump 
w^ould apparently work ; but really, the water piston would be 
dragging the steam piston along. 

Q. How may acids be pumped? A. By what is known as 
blowing up ; that is, b}^ employing a pump to put pressure upon 



580 HANDBOOK OX ENGINEERING. 

the acid in a closed vessel, thereby forcing it through a pipe 
placed in the bottom of the vessel. 

Q. In case anj^ wearing part of a pump gets to cutting, what 
should be done? A. If it is not practicable to stop the pump nor 
to reduce its speed, the part which is getting damaged should be 
given very liberal oiling. 

Q. What is the best oil for this purpose? A. That depends on 
the nature of the cutting surfaces, and on the pressure therein ; 
the mineral oils are generally more cooling than others, although 
they have less body to resist squeezing. 

CALCULATING THE BOILER FOR A STEAM PUMP. 

The amount of work which a boiler has to do is very easy of 
determination. Given the largest number of gallons which a 
pump will be required to pumj^ per minute, and the height in feet 
from the surface of the well from which the water is drawn, to 
the point of discharge, you can easily tell by multiplying by 8^ — 
the weight in pounds of one gallon — the number of foot pounds 
of power consumed per minute in lifting the water, adding a cer- 
tain percentage for friction of the machine and of water in the 
pipe, we have the total number of foot pounds consumed per 
minute, and this divided by 33,000 will be the horse power 
consumed. 

The allowance for friction will vary with the style, size and 
condition of the pump, the size of the pipe, and, above all, the 
manner in which the pipe is connected up, the number of right 
angle turns, etc. 

This may be arrived at in another way. A column of water 
2.3 feet in height exerts a j)ressure of one pound. Allowing the 
.3 for friction, we can, by dividing the total left in feet by two, 
get at the pressure per square inch, which is being exerted against 
the water piston or plunger, and multiplying by the number of 



HANDBOOK ON ENGINEERING. 581 

square inches in that piston gives the total pressure against which 
the pump is working. This multiplied by the piston speed in feet 
minutes, and divided by 33,000, will give the lift in horse power. 
In this case, as in the other, the lift must be calculated from the 
surface of the supply, and not from the pump, when the pump is 
lifting its supply. If the water flows to* the pump it must be 
calculated from the height of the water cylinder. An allowance 
of, say, 25 per cent, should be made above the horse power thus 
shown, in order to provide for contingencies, and to be on the 
safe side. 

In selecting a boiler to do this work, it must be borne in mind 
that a boiler which is sold for a certain horse power, is supposed 
to be able to furnish that power in connection with a good steam 
engine , and they are not apt to be overrated . Now , the steam pump 
as usually built, does not approach in economy the ordinary steam 
engine, and, therefore, a boiler which will develop twenty-five 
horse power in connection with a good engine would be too small 
for a pump which was required to do the same amount of work. 
The evaporation of 30 pounds of water per hour from feed at 100 
degrees Fahr. into steam of 70 lbs. pressure, has been adopted by 
several authorities as a horse power. Any good automatic cut-off 
will run on this amount of water, and if an estimate can be made 
of the comparative performance of the pump under consideration, 
a close approximation to the desired size of boiler can be made. 

THE WORTHINQTON WATER METER. 

The counter registers cubic feet ; one foot being 7^*^%^ gallons, 
United States standard. It is read in the same way as registers 
of gas meters. The following example and directions may be of 
use to those unacquainted with the method : If a pointer is 
between two figures, the smaller one must invariably be taken. 
Suppose the pointers of the dials to stand as in the engraving. 



582. 



HANDBOOK ON ENGINEERING. 



The reading is 6,874 cubic feet. From the dial marked ten tvc 
get the figure 4 ; from the next, marked hundred, the figure 7 ; 
from the next, marked thousand, the figure 8; from the next, 




marked ten thousand, the figure 6. The next pointer being 
between ten and 1, indicates nothing. By subtracting the read- 
ing taken at one time, from that taken at the next, the consump- 
tion of water for the intermediate time is obtained. 

TABLE OF PRESSURE DUE TO HEIGHT. 





QJ 








a> 




<x> 




OJ 




0) 




































. 




■. 




. 




S3 . 




fl . 




(3 . 




. 




JS -^ 




w -^ 




^ -^ 




JS -^ 




[^ -^ 




^ -^ 




m -^ 


'd 


n- ^ 


-d 


l-a 


-d 


2a 

ft 


IS 


£.3 

ft . 


-d 


ta 


-d 


1.3 


'd 






W ^ 


3S 


^^ 




CT" 


53 


.S- 








u.S' 




«S^ 




5 il 




=« jn 




OS ;h 




»* ^^ 




"^ Jn 




c« ;h 




^ '3 


^ 


^^ 


^ 


&^ 


CO 


&^ 


a> 


&ft 


0) 


&^ 


m 


&^ 


<o 


S^'P. 


N 


H 


1=. 


H 


tH 


1^ 1 


N 


H 


P^ 


li^ 


N 


W 


E^ 


s 


1 


0.34 


15 


6.49 


30 


12.99 


45 


19 49 


60 


25 99 


75 


32.48 


90 


38.98 


5 


2.16 


20 


8 66 


85 


15 16 


50 


21.65 


65 


28 15 


80 


34 65 


95 


41 15 


10 


4.33 


26 


10.82 


40 


17.32 


55 


23.82 


70 


30.32 


85 


36.82 


100 


43 31 



HANDBOOK ON ENGINEERING. 



583 



TABLE OF DECIMAL EQUIVALENTS OF 8ths, 16ths, 
32ds AND 64ths OF AN INCH. 



8ths. 


32ds. 


64ths. 


64ths. 


k = .125 


-3^ = 


.03125 


6h- = 


.015625 


II = 


.546875 


i = .25 




.09375 


6^ = 


,046875 


llZ 


.57H125 


1 = .375 


-A- = 


.15625 




.078125 


.609375 


i = .50 


zh== 


.21875 


-h = 


.109375 


I'i = 


.640625 


1 = .625 


h = 


.28125 


¥.= 


.140626 


64 = 


.671875 


1 = .75 


3 2 = 


.34375 




.171875 


]t = 


.703125 


I = .875 


i| = 


.40625 


64 = 


.203125 


.734375 




1| = 


.46875 


!t = 


.234375 


HE 


.765625 




AZ 


.53125 


.265625 


.796875 


16ths. 


.59375 


64 = 


.296875 


.828125 




32 = 


.65625 


f 4 = 


.328125 


t = 


.869375 


A- = .0625 


3I = 


.71875 


64 = 


.359375 


.890625 


A = 1875 


|4 = 


.78125 


If = 


.390625 


.921875 


A = .3125 


uz 


.84375 


I4 = 


.421875 


1" = 


.958125 


fe- = .4375 


.90625 


64 = 


.453125 


.984375 


-5g = .5625 


ll = 


.96875 


64 = 


.484375 






-i-^- = .6875 






64 


.515625 






if = .8125 














[| = .9375 















LATENT HEAT OF LIQUIDS, UNDER A PRESSURE 
OF 30 INCHES OF MERCURY. 

(TREATISE ON HEAT, BY THOMAS BOX.) 



Latent Heat 
in Units. 



Increase of Tempe- 
rature of Liquid, 
if Heat had not 
become Latent. 



Water 

Alcohol 

Ether 

Oil of Turpentine. 
Naphtha 



966 

457 
313 

184 

184 



966° 

735° 
473° 

390° 

443° 



Regnault. 
Ure. 



of 



The Boiling Point of different Liquids varies ; and the Boiling Point 
a liquid varies with the pressure. 



584 



HANDBOOK ON ENGINEERING. 



•*0»0.— i<X!(Mt^(M00COOO 



COCO<?^'^>— lOOCiOOOOO- 



l>'OC0»«Q0i-H^t>-05C<)»O 



OSt-WiCOi— tOSt'-OCOi— 100 
t>.i-t»005C0CC>O-*00<M»0 
C0C£>G0OC0>OC5OS0l0t>- 



(MCO-*ioi>.oooiO(rvjcoT»H 

r- ICOlCilr-Oi>— iCOC£iOOOC^l 



GO- CO »0 ■<*< CO (M O 05 GO »>• i£i 
OOOMTHCOQOOi-HCOlOb- 

rHc^c^isqcqcqcocccococo 



(Mb-.C000CCCOCOO5-<tiO5"* 
IflrHOOTH— «I>.'<*IOI<-COO 

<:ocooi.— leo-^oojosi-tco 

t-(i-ii-i(Mi:^(M(M(?qcqcOCO 



O5C0t>-'H »fiOiCO<X>0'*CO 
CCQOiMt>«i-Hir50-<*l05COt^ 



1— iifiOSCOt^.— ICOO^iHGOlM 
■*«O00— iCOCOOO'-ICOiOGO 
(MCC'*«?t^0Oa5>-H(MCO'* 



»£50«Cit'-QOCOO^OSOOi-« 
0.-ciNCO-#iC<Xit^050^ 



C0t^i:O»O'*(?q — 00500CD 
COt^COlO-slHCOtN-HOCWCD 

ooosO'— icgcO'^ioOtX't^ 



-+^QO'-l>0000»^OOCg>OGO 
COOCOiO(MOt^"*C<JOi«D 
l>.00G005O'-irH(MC0C0'<ti 



»OU5iX'':Ot-t>.Q0000505r 



(M OO 05 (M 



O (M 00 C^ 



t>- 00 «D «£> 



O «0 00 05 



00 '-^ l>. 00 



CO to lO — < 



fl * 2 
S' o o ^ 

^i; o 03 

® o ^ >^ 

O eS S P< 



cq o ci lo 



(M Oi OS IN 



o a> ao 00 



CO 



a 03 S a 



HANDBOOK ON ENGINEERING. 



o85 



CAPACITY OF SQUARE CISTERNS IN U. S. GALS. 





5X5 


5X6 


5X7 


5X8 
1496 


5X9 


5X10 


6X6 


6X7 


6X8 6X9 


6X10 


5 ft.. 


935 


1122 


1309 


1683 


1870 


1346 


1571 


1795 2020 


2244 


5ift.. 


1028 


1234 


1440 


1645 


1851 


2057 


1481 


1728 


1975 


2221 


2469 


6 ft.. 


1122 


1346 


1571 


1795 


2019 


2244 


1615 


1885 


2154 


2423 


2693 


6i ft. • 


1215 


1459 


1702 


1945 


2188 


2431 


1750 


2042 


2334 


2625 


2917 


7 fr.. 


1309 


1571 


1833 


2094 


2356 


2618 


1884 


2199 


2513 2827 


3142 


7^f'.. 


1403 


1683 


1963 


2244 


2524 


2800 


2019 


2356 


2693 3029 


3366 


8 ft.. 


1496 


1795 


2094 


2393 


2693 


2992 


2154 


2513 


2872 


3231 


3592 


Sift.. 


1589 


1907 


2225 


2543 


2861 


3179 


2288 


2670 


3052 


3433 


3816 


y ft.. 


1683 


2020 


2356 


2693 


3029 


3366 


2423 


2827 


3231 


3635 


4041 


9ift.. 


1776 


2132 


2487 


2842 


3197 


3553 


2558 


2984 


3412 


3837 


4265 


10 ft.. 


1870 


2244 


2618 


2992 


3366 


3470 


2692 


3142 


3591 


4039 


4489 




6X11 


6X12 


7X7,7X8 


7X9 


7X10 


7X11 


7X12 


8X8 


8X9 




5 ft.. 


2468 


2693 


1832 2094 


2356 


2618 


2880 


3142 


2394 


2693 




5i ft. . 


2715 


2962 


2016 2304 


2592 


2880 


3168 


3456 


2633 


2962 




6 ft.. 


2962 


3231 


2199,2513 


2827 


3142 


3456 


3770 


2872 


3231 




e^ft.. 


3209 


3500 


23822722 


3063 


3403 


3744 


4084 


3112 


3500 




7 ft.. 


3455 


3770 


2565 2932 


3298 


3665 


4032 


4398 


3351 


3770 




7ift.. 


3702 


4039 


2748 3141 


3534 


3927 


4320 


4712 


3590 


4039 




8 ft.. 


3949 


4308 


2932 3351 


3770 


4189 


4608 


5026 


3830 


4308 




Sift.. 


4196 


4577 


3115'3560 


4005 


4451 


4896 


5340 


4069 


4578 




9 ft.. 


4443 


4847 


32983769 


4341 


4712 


5184 


5655 


4308 


4847 




9ift.. 


4689 


5116 


348l|3979 


4576 


4974 


5472 


5969 


4548 


5116 




10 ft.. 


4936 


5386 


3664 


4188 


4712 


5236 


5760 


6283 


4788 


5386 





WEIGHT OF WATER. 



1 cubic inch 03617 pound. 

12 cubic inches 434 pound. 

1 cubic foot (salt) 64.3 pounds. 

1 cubic foot (fresh) 62.425 pounds. 

1 cubic foot 7.48 U. S. Gallons. 

Note. — The center of pressure of a body of water is at two-thirds 
the depth from the surface. 

To find the pressure in pounds per square inch of a column of water, 
multiply the height of the column in feet by .434. Every foot elevation 
is called (approximately) equal to one-half pound pressure per square 
inch. 



586 



HANDBOOK ON ENGINEERING. 



SHOWING U. S. GALLONS IN GIVEN NUMBER OF 
CUBIC FEET. 



Cubic 
Feet. 


Gallons. 


Cubic 
Feet. 


Gallons. 


Cubic Feet. 


Gallons. 


0.1 


0.75 


50 


374.0 


9,000 


67,324.6 


0.2 


1.50 


60 


448.8 


10,000 


74,805.2 


0.3 


2.24 


70 


523.6 


20,000 


149,610.4 


0.4 


2.99 


80 


598.4 


30,000 


224,415.6 


0.5 


3.74 


90 


673.2 


40,000 


299,220.7 


0.6 


4.49 


100 


748.0 


50,000 


374,025.9 


0.7 


5.24 


200 


1,496.1 


60,000 


448,831.1 


0.8 


5,98 


300 


2,244.1 


70,000 


523 636.3 


0.9 


6.73 


400 


2,992.2 


80,000 


598,441.5 


1 


7.48 


500 


3,740.2 


90,000 


673,246.7 


2 


14.9 


600 


4,488.3 


100,000 


748,051.9 


3 


22.4 


700 


5,236.3 


200,000 


1,496,103.8 


4 


29.9 


800 


5,984.4 


300,000 


2,244,155.7 


5 


37.4 


900 


6,732.4 


400,000 


2,992,207.6 


6 


44.9 


1,000 


7,480.0 


500,000 


3,740,269.5 


7 


52.4 


2,000 


14,961.0 


600,000 


4,488,311.4 


8 


59.8 


3,000 


22,441.5 


700,000 


5,236 363.3 


9 


67.3 


4,000 


29,922.0 


800,000 


5,984,415.2 


10 


74.8 


5,000 


37,402.6 


900,000 


6,732,467.1 


20 


149.6 


6,000 


44,883.1 


1,000,000 


7,480,519.0 


30 


224.4 


7,000 


52,363.6 






40 


299.2 


8,000 


59,844.1 







From the above any cubic feet reading can readily be converted into 
U. S. gallons, as follows: 

How many gallons are represented by 53,928 cubic feet? 

50,000 cubic feet = 374,025.9. gallons. 

3,000 '^ '' = 22,441.5 « 

900 " *' = 6,732.4 «« 

20 " '^ = 149.6 " 

8 ^' " = 59.8 « 



53,928 cubic feet = 403,409.2 gallons. 



HANDBOOK ON ENGINEERING. 



587 



SHOWING COST OF WATER AT STATED RATES 
PER lOOO GALLONS. 



Number 

of 

Cubic 

Feet. 






COST PER 


1000 GALLONS. 






5 


6 


8 


10 


15 


20 


25 


30 


Cents. 


Cents. 


Cents. 


Cents. 


Cents. 


Cents. 


Cents. 


Cents. 


20 


$0 007 


$0,009 


$0,012 


$0,015 


$0,021 


$0,030 


$0,037 


$0,045 


40 


0.015 


0.018 


0.024 


0.030 


0,045 


060 


0.075 


0.090 


60 


0.022 


0.027 


0.036 


0.045 


0.066 


0.090 


0.112 


0.135 


80 


0.030 


0.036 


0.048 


0.060 


0.090 


0.120 


0.150 


0.180 


100 


0.037 


0.049 


0.060 


0.075 


0.111 


0.150 


0.187 


0.224 


200 


0.075 


0.090 


0.f20 


0.150 


0.225 


0.299 


0.374 


0.449 


300 


0.112 


0.135 


0.180 


0.224 


0.336 


0.449 


0.561 


0.673 


400 


0.150 


0.180 


0.239 


0.299 


0.450 


0.598 


0.748 


0.898 


500 


0.188 


0.224 


0.299 


0.374 


0.564 


0.748 


0-935 


1.122 


600 


0.224 


0.269 


0.359 


0.449 


0.448 


0.898 


1.122 


1.346 


700 


0.262 


0.314 


0.419 


0.524 


0.786 


1.047 


1-309 


1-571 


800 


0.299 


0.350 


0.479 


0.598 


0.897 


1.197 


1.496 


1-795 


900 


0.337 


0.404 


0.539 


0.673 


1.011 


1 346 


1.683 


2.020 


1,000 


0.374 


0.449 


0.598 


0.748 


1.122 


1.496 


1.870 


2.244 


2,000 


0.748 


0.898 


1.197 


1.493 


2.244 


2.992 


3-740 


4-488 


3,000 


1.122 


1.346 


1-795 


2.244 


3.366 


4.488 


5.610 


6.732 


4,000 


1.496 


1.795 


2.393 


2.992 


4.488 


5.984 


7.480 


8.976 


5,000 


1.870 


2.244 


2.992 


3-740 


5.610 


7.480 


9-350 


11-220 


6,000 


2.244 


2.692 


3.590 


4.488 


6.732 


8.976 


11.220 


13-464 


7,000 


2.618 


3.141 


4.189 


5.236 


7.854 


10.472 


13.090 


15.708 


8,000 


2.992 


3.590 


4.787 


5.984 


8.976 


11.9«8 


14.961 


17-953 


9,000 


3.366 


4.039 


6.385 


6.732 


10.098 


13.464 


16.831 


20-197 


10,000 


3.74 


4.488 


5.984 


7-480 


11.122 


14.961 


18.701 


22.441 


20,000 


7.48 


8.976 


11.968 


14.961 


22.443 


29.992 


37-402 


44.882 


30,000 


11.22 


13.46 


17.95 


22.44 


33.664 


44.88 


56.10 


67.32 


40,000 


14.96 


17.95 


23.94 


29.92 


44.885 


59.84 


74.10 


89.77 


50,000 


18.70 


22.44 


29.92 


37.40 


56.103 


74.80 


93-50 


112.20 


60,000 


22.44 


26.92 


35.90 


44.88 


67.323 


89.76 


112.20 


134-64 


70,000 


26.18 


31.41 


41.89 


52.36 


78.543 


104.72 


130.90 


157-08 


80,000 


29.92 


35.90 


47.87 


59.84 


89.766 


119.68 


149.61 


179.53 


90,000 


33.66 


40.39 


53.85 


67.32 


100.986 


134 64 


168-31 


201.97 


100,000 


37.40 


44.88 


59.84 


74.80 


111.22 


149.61 


187-01 


224.41 


200,000 


74.81 


89.76 


119.68 


149.61 


224.43 


299 22 


374.02 


448.82 


300,(100 


112.20 


134.64 


179.53 


224.41 


336.64 


448.83 


561.03 


673.24 


400,000 


149.61 


179.53 


239.37 


299.22 


448-85 


598.44 


748.06 


897.66 


500,000 


187.01 


224.41 


299.22 


374.02 


561-03 


748.05 


935.06 


1122.07 


600,000 


224.41 


269.29 


359.06 


448 83 


673.23 


897.66 


1122.07 


1346.49 


700,000 


261.81 


314.18 


418.90 


523.63 


785.43 


1047.27 


1309.08 


1570.88 


800,000 


299-22 


359.06 


478.75 


598.44 


897-66 


1196 88 


1496.10 


1795.32 


900,000 


336.62 


403.94 


538.59 


673.24 


1009-86 


1346.49 


1683-11 


2019.73 


1,000,000 


374.02 


448.83 


598.44 


748.05 


1122.06 


1498.10 


1870.12 


2244.15 



HANDBOOK ON ENGINEERING. 



H 

m 



7 

SI 

j 






































d • d 


i 

o 


■o 




107 
150 
204 
0.263 
0.333 
0.408 


o 

M 




































d -d) 


d ;© 


0.188 
267 
0.365 
0.472 
0.593 
0.730 






































d ;© 


O ;d 


362 
515 
697 
0.910 
































o 

o 


0.02 

0.04 
0.08 
0.13 
20 
0.29 
0.38 
0.49 
63 
0.77 
1.11 






a 

M 




























o o o d o d d d d © o -^ 




































07 
0.09 
12 
16 
0.20 
25 
0.53 
0.94 
1.46 
2.09 






























© 


0.10 

""o.ii 

0.26 
0.37 
0.50 
65 
0.81 

2 21 

3.88 














i 
















d 


d 


§ :^^^^^^^^ : ; 














J5 
eo o 






s 








74 
1.31 
1.99 
2.85 
3.85 
5.02 
7.76 
11.2 
15 2 
19.5 
25.0 
30.8 














^1 






d 








0.81 
1 80 

3 20 

4 89 
7.0 
9.46 

12.47 
19.66 
28.06 




















:2 :^ 
:d jo 


d 


§ 


2.44 
5.32 
9.46 
14.9 
21.2 
28 1 
37 5 
























0.12 
0.47 
0.97 

1 66 

2 62 

3 75 
5.05 
6.52 
8 15 

10.0 
22.4 
39 






























0.31 

1 05 

2 38 
4.07 
6 40 
9.15 

12.4 
16 1 
20.2 
24.9 
56.1 






























"1 


84 
3.16 
6 98 
12 3 
19.0 
27.5 
37 
48.0 


































3.3 

13 

28.7 
50 4 
78.0 






































•85 


aufoi 


oc 


»ftC 


ir 


? 


S 


r 




? 


lO 


1 


I 


- 


r^c 


s 




" 


II 


s^ll 


1 


gl 


? 

S 


iiii 


§ 


i 



HANDBOOK ON ENGINEERING. 



589 



SHOWING HOW WATER MAY BE WASTED. 

GALLONS DISCHARGED PER HOUR THROUGH VARIOUS SIZED ORIFICES 
UNDER STATED PRESSURES. 



a 


ja 13 0) 


Diameters of Orifices in 


Inches and Fractions of an 


Inch. 


^t 






















Qi pq 


o « b 


i 


§ 


* ■ 


§ 


i 


1 


H 


H 


1^ 


2 


inch 


inch 


inch 


inch 


inch 


inch 


inch 


inch 


inch 


inch 


20 


8.66 


300 


720 


1260 


1920 


2760 


4920 


7380 


11100 


15120 


19740 


40 


17.32 


450 


960 


1800 


2760 


3960 


6720 


10920 


15720 


21360 


27960 


60 


25.99 


640 


1200 


2160 


3480 


4800 


8580 


13380 


19200 


26220 


34260 


80 


34.65 


*620 


1380 


2460 


3840 


5580 


9840 


15480 


22260 


30300 


39540 


100 


43.31 


690 


1560 


2760 


4320 


6240 


11040 


17280 


24900 


33900 


44280 


120 


51.98 


780 


1780 


3000 


4740 


6840 


12120 


18960 


27240 


37440 


48480 


UO 


60.64 


816 


1860 


3300 


5100 


7320 


13020 


20160 


29460 


39080 


52320 


150 


64.97 


840 


1920 


8420 


5280 


7620 


13560 


21180 


30480 


41460 


54120 


175 


75.80 


900 


2040 


3660 


5700 


8220 


14640 


22800 


32880 


44940 


58560 


200 


86.63 


960 


2220 


3900 


6120 


8760 


15600 


25020 


35880 


47880 


62580 


235 


101.79 


1080 


2460 


4320 


8280 


11160 


17100 


26760 


38520 


52260 


68460 



The pressure or head of water is taken at the orifice, no allowance 
being made for friction in the pipe. In practical calculations to deter- 
mine the height which water can be thrown, the head consumed by the 
friction of the water in flowing from the source to the orifice must be 
considered. 



IGNITION POINTS OF VARIOUS SUBSTANCES. 



Phosphorus ignites at 

Sulphur 

Wood 

Coal 



150° 
500° 
800° 
1000° 



Lignite, iu the form of dust, ignites at 150° 

CannelCoal, - '^ " '' 200° 

Coking Coal, '' '- '' '' . 250° 

Anthracite, '' " '' "... 300° 



590 



HANDBOOK ON ENGINEERING. 



CONTENTS IN CUBIC FEET AND IN U. S. GALLONS. 

(from trautwein) 

Of 231 cubic inches (or 7.4805 gallons to a cubic foot) ; and for one foot of length of 
the cylinder. For the contents for a greater diameter than any in the table take 
quantity opposite one-^ai!/ said diameter, and multiply it by 4. Thus, the number 
of cubic feet in one foot length of a pipe 80 inches in diameter is equal to 
8.728x4=34.912 cubic feet. So also with gallons and areas. 





o 


For 1 foot in 






For 1 foot in 




o 


For 1 foot in 


c 




length. 


C 


'11 o 


length. 


a 


fl5 


length. 


11 


n 




mj2 . 


|| 


OP'S o 




o 




-go 






II 


11 

-a 




ip 

o 


il 


5| 


<0 03 ® 

Sis 

fl S s 


o 


11 




Oj c3 © 




h 


.0208 


0003 


.0026 


1 


.5625 


.2485 


1.859 


19. 


1.583 


1 969 


14.73 


5-16 


.0260 


.0005 


.0040 


7. 


.5833 


.2673 


1 999 


h 


1.625 


2 074 


15 52 


% 


-0313 


.0008 


.0057 


1 


.6042 


.2868 


2 144 


20. 


1.666 


2.182 


16.32 


7-16 


.0365 


0010 


.0078 


.6250 


.3068 


2.295 


1 


1.708 


3.292 


17.15 


h 


.0417 


.0014 


.0102 


1 


.6458 


.3275 


2.450 


21. 


1 750 


2 405 


17 99 


9-16 


.0469 


.0017 


.0129 


S. 


6667 


.3490 


2.611 


h 


1.792 


2.521 


18.86 


11-16 


.0521 


0021 


.0159 


. 


.6875 


.3713 


2 777 


22. 


1 833 


2.640 


19.75 


.0673 


.0026 


.0193 




.7083 


.3940 


2 948 


h 


1,875 


2.761 


20.65 


1 


.0625 


.0031 


.0230 




.7292 


.4175 


3.125 


23.' 


1.917 


2.885 


22.58 


13-16 


.0677 


0031 


.0270 


9.* 


.7500 


.4418 


3 305 


h 


1.958 


3 012 


31.53 


1 


.0729 


.0042 


0312 


i 


.7708 


.4668 


3 492 


24. 


2.000 


3 142 


23.50 


15-16 


.0781 


.9048 


0359 


h 


.7917 


.4923 


3 682 


25. 


2.083 


3.409 


25.50 


1. 


.0833 


C055 


.0408 


1 


.8125 


.5185 


3.879 


26. 


2.166 


3.687 


27.58 


^ 


.1042 


.0085 


.0638 


10. 


.8333 


.5455 


4 081 


27. 


2.250 


3.976 


29.74 


X 


.1250 


-0123 


.0918 


i 


8542 


.5730 


4.286 


28. 


2 333 


4.276 


31.99 


1 


.1458 


.0168 


1250 


1 


.8750 


.6013 


4.498 


29. 


2 416 


4 587 


34.31 


2. 


.1667 


.0218 


.1632 


1 


.8958 


.6303 


4.714 


30. 


2.500 


4.909 


36.72 


1 


.1875 


.0276 


.2066 


11. 


.9167 


.6600 


4.937 


31. 


2 583 


5.241 


39.21 


.2083 


.0341 


.2650 


1 


.9375 


.6903 


5.163 


32. 


2.666 


5.585 


41.78 


1 


.2292 


.0413 


.3085 


t 


9583 


.7213 


5 395 


33. 


2.750 


5.940 


44.43 


3. 


.2500 


.0491 


.3673 


1 


.9792 


.7530 


5.633 


34. 


2.833 


6.306 


47.17 




.2708 


.0576 


.4310 


12.* 


1 Foot. 


.7854 


5.876 


35. 


2.916 


6.681 


49.98 


1 


.2917 


.0668 


.4998 


h 


1.042 


.8623 


6.375 


36. 


3.000 


7.069 


52.88 


1 


.3125 


.0767 


.5738 


13. 


1.083 


.9218 


6.896 


37. 


3.083 


7.468 


55.86 


4. 


.3333 


.0873 


.6528 


h 


1.125 


.9940 


7.435 


38 


3 166 


7.876 


58.92 


1 


.3542 


.0985 


.7370 


14. 


1.167 


1.069 


7.997 


39. 


3 260 


8 296 


62.06 


.3750 


.1105 


.8263 


k 


1.208 


1.147 


8.578 


40. 


3.333 


8.728 


65.29 


a 


.3958 


.1231 


.9205 


15. 


1.250 


1.227 


9.180 


41. 


3.416 


9.168 


68.58 


5. 


.4167 


.1364 


1.020 


k 


1.292 


1.310 


9.801 


42. 


3.500 


9.620 


71.96 


i 


.4375 


.1503 


1.124 


16. 


1.333 


1.396 


10.44 


43 


3. 583 


10.084 


75.43 


i 


.4583 


1650 


1.234 


h 


1.375 


1.485 


11.11 


44. 


3 666 


10.560 


79.00 


1 


.4792 


.1803 


1.349 


17. 


1.417 


1.576 


11.79 


45. 


3.750 


11.044 


82 62 


6. 


.5000 


.1963 


1.469 


h 


1.458 


1 670 


12.50 


46. 


3.833 


11.640 


86.32 


f 


.5208 


.2130 


1.594 


18. 


1.500 


1.767 


13.22 


47. 


3.916 


12 048 


90.12 


.5417 


.2305 


1.724 


h 


1.542 


1.867 


13.97 


48. 


4.000 


12.566 


94.02 



HANDBOOK ON ENGINEERING. 591 



CHAPTER XX, 
THE INJECTOR AND INSPIRATOR. 

The energy of motion of a body is well known to be the prod- 
uct of its mass by the half square of its velocity ; hence, it is 
possible to communicate to a body of little weight a large amount 
of energy by moving it fast enough, and in fact, the energy of 
motion would only be limited by the speed which can be given 
the body. In this way a small weight of steam flowing from an 
orifice into a properly shaped jet of water is condensed, while the 
velocity of the steam is greater than if flowing into air ; the 
energy thus communicated is made sufllciently great by increasing 
the weight of steam, which can be done by increasing the area of 
the steam way, until we find such jet pumps adapted to many 
purposes. There are, however, two which are of interest to us 
in this connection, the well-known injector and inspirator, with 
the large family of lifting and non-lifting varieties, all differing 
in details as to form of nozzles, area of passages, distances 
between nozzles, and that class of instruments in which, after a 
certain energy and velocity have been reached, the operation is 
repeated. These might be called " consecutive " instruments. 
The illustrations in this book show some of the simplest and 
adjustable kinds. Within a few years the principle of increase of 
energy by increase of mass or velocity has been applied by in- 
creasing the mass of steam used until we find that not only can a 
few pounds weight of steam put into a boiler a good many more 
pounds of water at a much higher temperature than it had, but 
that in a non-condensing engine it is possible, by using the ex- 
haust in part, to put into the boiler at a much higher pressure 



592 HANDBOOK ON ENGINEERING. 

and temperature, a weight of water which is still greater thau 
that of the steam moving it. 

When the injector first made its appearance it was, by many, 
considered as almost a paradox, especially by those who looked 
at the question as one of hydrostatics only. That steam from a 
boiler could put water back into it at the same pressure, and over- 
come the friction of the passages without the aid that a steam 
pump had of a difference of piston areas, was to them a puzzle. 
The use of exhaust steam at atmospheric pressure for the purpose 
of putting water into a boiler at a pressure of 150 lbs. per square 
inch, would be to such minds utterly incomprehensible. The use 
of an injector and inspirator, has this to recommend them, that 
the feed-water cannot be introduced into the boiler cold or nearly 
so, but must be warmed by contact with the steam, and the value 
of this has been already shown. In small boilers where no heater 
is used, an exhaust injector is better than a pump, and so is an 
ordinary injector ; but the former includes in itself an exhaust 
heater, saving a portion of heat from the exhaust, besides taking 
the power as heat also ; while, with the common injector, the 
heat for power and raising temperature are both derived from the 
live steam in the boiler. The latter portion of heat is, of course, 
directly returned to the boiler without loss, but that for j^ower is 
necessarily expended. As to the amount of power used by pump 
and injector compared with each other, it would seem that the 
pump is most efficient. There have been many comparative trials 
of pump and injector, but the results have usually been unsatis- 
factory from contained discrepancies. 

RANGE OF THE INSPIRATOR AND INJECTOR. 

The steam pressure at which an injector will start and the 
highest steam pressure at which it will work constitute what is 
termed the " range " of an injector, and the inspirator varies with 
the vertical lift and the temperature of the feed water. 



HANDBOOK ON ENGINEERING. 



593 



It must also be borne in mind that the same style of construc- 
tion in an injector and inspirator, while it confines them to about a 
specific range between its lowest starting and highest working points, 
jjermits of variation as to what the lowest starting point shall be. 
A style of construction which gives a range (on say a 2-foot lift) 
of 25 lbs. to 155 lbs. would permit of a range of 35 lbs. to 165 
lbs. (in fact, to a little higher than 165 lbs.). Different manu- 
facturers, therefore, vary as to the starting point in their stand- 
ard machines — aiming to cover the range which they deem most 
desirable. Nearly all have adopted about 25 lbs. on a 2-foot lift, 
as lowest starting point. 




The World. 



POSITIVE OR DOUBLE TUBE INJECTORS. 

As before stated, this class of injector is provided with two sets 
of tubes or jets, one set adapted to hft the water and deliver it to 



594 HANDBOOK ON ENGINEERING. 

the second set, which forces the water into the boiler. By this 
arrangement, it is apparent that inasmuch as the hfting jets 
supply a proportionate amount of water with varying steam pres- 
sures, a wider range is obtainable than with an automatic in- 
jector. In the following cases, it is better to use the double tube 
injectors : — 

1. Where the feed water is of too high a temperature to be 
handled by the automatic injectors. 

2. When a great range of steam variation is accompanied by 
the condition of a long lift. 

The World Injector is one of the best and most popular of the 
double tube type of injectors. It is entirely self contained. It 
is supplied even with its own check valve and operated entirely 
by a single lever, a quarter of a turn of which starts the lifting, 
after which the completion of the single revolution sets the injector 
working to boiler. , 

GENERAL SUGGESTIONS FOR PIPING=UP INJECTORS AND 
INSPIRATORS AND SUGGESTIONS THAT SHOULD BE 
CAREFULLY FOLLOWED WHEN MAKING PIPE CONNEC= 
TIONS. 

Steam* — Connect steam pipe with highest parts of boiler and 
never connect with a steam pipe used for any other purpose. I 
would recommend a globe valve being placed in the steam pipe 
next to boiler which can be closed in case it is desired to take off 
the injector. At all other times it can be left open. When the 
steam connection is made, be sure and take off the injector before 
the steam is turned on the machine. Then blow out the steam 
pipe with at least forty pounds steam, which will remove all dirt 
and scale. 

Suction* — This pipe must be tight, and if there is a valve in it 
the stem must be well packed. 

To test the suction pipes for leaks, plug up the end of the pipe 



HANDBOOK ON ENGINEERING. 595 

and then screw on a common iron cap on the overflow ; or if you 
do not have one, unscrew cap X, and place a piece of wood on 
top of valve P ; replace the cap and the wood will hold the valve 
from rising ; then turn on the steam which will locate all leaks. 



All pipeSt whether steam, suction or delivery, must be of the 
same or greater size than the corresponding branch of each injec- 
tor. Have all piping as short and as straight as possible, and 
especially avoid short turns. 



59 fi HANDBOOK ON ENGINEERING. 

If any old pipe is used, see that it is not partially filled or 
stopped up with rust. 

If the injector or inspirator has to lift the water very high or 
draw it very far, have the suction pipe a size or two larger than 
called for by the suction branch of the injector or inspirator. 

Have the water supply (suction) pipe independent of any other 
connection. The suction pipe must be absolutely air tight ; the 
slightest leak, in most cases, will prevent the injector or inspirator 
from forcing water into the boiler. 

Always place a globe valve in the suction pipe as close to the 
injector as possible, and place it so that it will shut down against 
the water side and see that the stem is packed tight. 

When using the injector or inspirator as non-lifting, put two 
globe valves in the suction, one close to the injector, the other as 
far from it as you can conveniently, keeping the one farthest from 
the injector or inspirator tolerably close throttled. This will 
surely repay you for your trouble. The check valve may be next 
to boiler with a valve between it and boiler, the further from 
injector the better. If the injector forces through a heater, place 
check valve between injector and heater. , Also place a valve 
between heater and check valve so you can take check valve out 
if necessary. 

Size of pipes* — If injector or inspirator has over 10 feet lift, 
or a long draw, use suction pipe from strainer to valve a size 
larger than the connection on injector, reducing when you reach 
the valve. 

In all other cases, use for all pipes same size as injector 
connection. 

Blow-off* — Always blow out steam thoroughly before con- 
necting INJECTOR, so as to rciuove any dirt, rust or scale that 
may be in the pipes. 

Caution. — The suction pipe must be absolutely tight 
throughout. To make sure that it is so, test the suction as directed. 



HANDBOOK ON ENGINEERING. 597 

DIRECTIONS FOR CONNECTING AND OPERATING THE 
HANCOCK INSPIRATOR. 

** Stationary ** Pattern* — Connect as shown by cut above 
steam, suction and delivery. For full instructions, see page 588. 



^or a lift of 5 ft. 


, 15 lbs. steam pressure is required. 


10 '' 


20 " " " " 


15 " 


25 " " " " 


u u 20 " 


35 " " *' " 


25 " 


45 ic u (( u 



Operation* — Open overflow valves Nos. 1 and 3 ; close forcer 
steam valve No. 2 and open the starting valve in the steam pipe. 
When the water appears at the overflow, close No. 1 valve ; open 
No. 2 valve one-quarter turn and close No. 3 valve. The inspir- 
ator will then be in operation. 

Note. — No. 2 valve should be closed with care to avoid damag- 
ing the valve seat. When the inspirator is not in operation, both 
overflow valves Nos. 1 and 3 should be open to allow the water to 
drain from it. No adjustment of either steam or water supply is 
necessary for varying steam pressures, but both the temperature 
and quantity of the delivery water can be varied by increasing or 
reducing the water supply. The best results will be obtained 
from a little experience in regulating the steam and water supply. 
If the suction pipe is filled with hot water, either cool off both it 
and the inspirator with cold water, or pump out the hot water by 
opening and closing the starting valve suddenly. To locate a leak 
in the suction pipe, plug the end, fill it with water, close No. 3 
valve and turn on full steam pressure. Examine the suction pipe 
and the water will indicate the leak. If the inspirator does not 
lift the water properly, see if there is a leak in the suction pipe. 
Note if the steam pressure corresponds to the lift as above speci- 
fied, and if the sizes of pipe used are equal in size to inspirator 
connections. If the inspirator will lift the water, but will not de- 
liver it to the boiler, see if the check valve in the delivery pipe is 



598 



HANDBOOK ON ENGINEERING. 



in working order and does not " stick." Air from a leak in the 
suction connections, will prevent the inspirator from delivering 
the water to the boiler, even more than it will in lifting it only. If 
No. 1 valve is damaged, or leaks, the inspirator will not work 
properly. No. 1 valve can be easily removed and ground. 

THE HANCOCK STATIONARY INSPIRATOR. 





Suction. 



3 l^tE^ 'CEtD^ 

Overflow. 

To remove scale and deposits from inspirator jets or parts, 
disconnect the inspirator and plug both the suction and delivery 
outlets with corks. Open No. 2 valve and fill the inspirator with 
a solution of one part muriatic acid and ten parts water. Allow 
this solution to remain in the inspirator over night, then wash it 
thoroughly in clear water. 

Note. — It is not generally necessary to return an inspirator 
for repairs. The repair parts requirea can be ordered and the 
inspirator readily put in order. 



HANDBOOK ON ENGINEEKING. 599 



TO DISCOVER CAUSE OF DIFFICULTIES. 

WHEN INJECTOR FAILS TO GET THE WATER. 

1. The supply may be cut off by: (a) Absence of water at the 
source, (b) Strainer clogged up. (c) The suction pipe, hose 
or valve stopped up ; or if a hose is used, its lining may be loose 
(a frequent cause of trouble). 

2. A large leak in the suction (note that a small leak will pre- 
vent injector from working, but not from getting the water). 

3. Suction pipe or water very hot. Open drip-cock, turn 
steam on slowly, then shut it off quickly. This will cause the 
cool air to rush into the suction pipe and cool it off. Repeat if 
necessary. 

4. Lack of steam pressure for the lift; or, in some instances, 
too much steam pressure. If the steam pressure is very high, the 
injector will get the water more readily if the steam is turned on 
slowly and the drip-cock left open until the water is got. 

IF THE INJECTOR GETS THE WATER BUT DOES NOT FORCE IT TO 
THE BOILER, 

1. No globe valve on the suction with which to regulate the 
water, or else the supply water not properly regulated. 

2. Dirt in delivery tube. 

3. Faulty check valve. 

4. Obstruction between injector and check valve, or between 
check valve and boiler. 

5. Small leak in suction pipe admitting air to the injector 
along with the supply water. It is ten to one this is the cause of 
the difficulty every time. 

6. Be sure you understand the directions for starting before 
you condemn the injector. 



600 



HANDBOOK ON ENGINEERING. 



IF THE INJECTOR STARTS BUT " BREAKS." 

1. Supply water not properly regulated. If too much water, 
the waste or overflow will be cool ; if too little, the water will be 
very hot. 

2. Leaky supply pipe admitting air to the injector. It is ten 
to one this is the cause of difficulty. The suction must be air 
tight ; test as directed. 



MODE or 

CONNECTING 




The above illustration shows the mode of connecting the Pen- 
berthy Injector. 

3. Dirt or other obstruction, such as Time, etc., in delivery 
tube. 

4. Connecting steam pipe to pipe conducting steam to other 
points besides the injector, or not having suction pipe inde- 
pendent. 



HANDBOOK ON ENGINEERING. 



601 



5. Sometimes a globe valve is used on the suction connection 
that has a loose disc, and after starting the disc is drawn down, 
thus partially closing the valve; it is, of course, equivalent to 
giving the injector too little water. To remedy this, take the 
globe valve off and reverse it end for end. 

To clean* — To clean injector, unscrew plug 0, and the re- 
movable jet Y (which rests in it) will follow the plug out. 
Turn on steam (not less than forty pounds) and all dirt will be 
blown out. Examine all passages and drill holes and see that no 
dirt or scale has lodged in them. Replace jet by setting it in the 
plug (which acts as a guide) and screw into place tightly. Be 
careful not to bruise any jets, and use no wrenches on body of 
injector. 




WATE^ SUPPLY 



To test for leaks. — Plug up end of water supply pipe, then 
fit a piece of wood into cap Z, so that when screwed down it will 
hold the valve P in place, then turn on steam and it will locate 
leak. Do 7iot fail to do this in case of any troiible. 



TO START AND STOP INJECTOR. 

To start* — Open full the globe valve in water supply first, 
and then globe valve in steam pipe loide opeii. If water issues 
from overflow, throttle the valve ^ until discharge stops. Reg- 



602 



HANDBOOK ON ENGINEERING. 



ulate injector with water supply valve, not by steam valve. 
When water supply is above the injector, in starting open steam 
valve first. 

To stop^ — Close the steam valve. The water valve iZ" need 
not be closed unless the injector is used as a non-lifter, or lift is 
considerable. 

PRICE LIST, CAPACITY, HORSE POWER, ETC. 



Pipe Connections. 



Capacity per Hour. 

1 to 4 ft lift, 50 to 75 

lbs. Pressure. 



Horse 
Power. 



oo 


$16 00 


A 


18 00 


A A 


20 00 


B 


25 00 


BB 


30 00 


C 


40 00 


cc 


45 00 


D 


55 00 


DD 


60 00 


E 


75 00 


EE 


90 00 


F 


110 00 


FF 


125 00 



Steam. Suction. Delivery, 



f 


■ 


§ in 














1 




1 " 


1 




1* " 


u 


u 


n " 








11 




1? .< 








2 




2 ' 


2 


2 


2 " 



Maximum. 
80 gal. 

120 •• 

165 

250 

340 

475 

575 

750 

920 
1300 
1740 
2270 
2820 



Minimum. 
55 gal. 

70 " 



300 
350 
4110 
500 
700 
900 
1100 
1400 



4 to 
8 to 
10 to 
15 to 
25 to 
35 to 
50 to 
60 to 
95 to 
120 to 
165 to 
230 to 
290 to 



35 
50 

60 
95 
162 
150 
230 
290 



HANDBOOK ON ENGINEERING. f)03 

To find the number of gallons of water delivered by a steam 
pump in one minute, when the diameter and stroke of water 
piston, and the number of strokes per minute are given : — 

Rule. — Square the diameter of water i3iston and multiply the 
result by .7854. Multiply this product by the stroke of the 
water piston in inches ; and multiply this product by the number 
of strokes per minute, and divide the result by 231. 

Example* — How many gallons of water per minute will a 
steam pump deliver, whose water cylinder is 6 inches in diameter 
and 12 inches stroke, making 60 strokes per minute? 

Ans. 88.128 galls. 

Operation : 6 X ^ X .7854 28.2744. 

28.2744 X 12 X 60 
And, 231 = 88.128. 

To find the relative proportion between the steam and water 
pistons. 

Rule* — Multiply the area of the pump piston by the resistance 
of the water in pounds per square inch ; and divide the product 
by the pressure of steam in pounds per square inch. The quotient 
will give the area of steam piston in square inches to balance the 
resistance. To this quotient add from 30 to 100 per cent of it- 
self, — depending on the speed of the pump, — and divide the 
sum by .7854, and extract the square root of the quotient for the 
diameter of the steam piston. 

Example* — What should be the diameter of the steam piston 
to force water against a pressure of 125 pounds per square inch, 
the diameter of water piston being 6 ins. and the steam pressure 
60 lbs. per square inch? Ans. lOJ inches. 

Operation: Q XQ .7874 = 28.2744 sqr. ins. 

And, 28.2744 X 125 = 3534.3 pounds the total resistance. 

3534.3 
Then, — ^ — z= 58.9 square inches the area of steam piston. 



604 HANDBOOK ON ENGINEERING. 

We will add 50 per cent for frictiou iu pump and in delivery 
pipe, and for a moderate speed of pump. 
Then, 58.9 X .50 = 29.45. 
And, 58.9 + 29.45=88.35, 

88.35 
And, ^ p. = 112.49 sqr ins.- 



Then, ^y 112.49 = 10.6 ins. the diameter of the steam piston. 

To find the pressure against which a pump can deliver water, 
when the diameter of steam piston, pressure of steam in pounds 
per square inch, and diameter of water piston are given: — 

Rule* — Multiply the area of steam piston by the pressure of 
steam in pounds per square inch, and divide the product by the 
area of the pump jjiston, and deduct from 30 to 50 per cent for 
friction in the delivery pipe and in the pump itself. 

Example* — The area of the steam piston is 112 square inches, 
and the area of water piston is 28 square inches, and the steam 
pressure is 60 lbs. per square inch, against what pressure can the 
pump deliver water, the resistance from friction being 48 per cent? 

Ans. 125 lbs. per sqr. in., nearly. 

112X60 
Operation : 28 =240. 

And, 240 X -48 = 115.20. 
Then, 240 — 115.20 = 124.8. 

To find the steam pressure required when the diameter of the 
steam i^iston, the diameter of the water piston, and the resistance 
against the pump in pounds per square inch are given : — 

Rule* — Multiply the area of water piston by the resistance on 
the pump in pounds per square inch, and divide the product by 
the area of the steam piston. 



HANDBOOK ON ENGINEERING. 605 

Example* — The resistance against the pump, including fric- 
tion, is 240 pounds per square incli. The area of steam piston 
is 112 square inches, and the area of water piston is 28 square 
inches. What pressure of steam is required to operate the pump ? 

Ans. 60 lbs. per sqr. in. 

Operation: — -— — =60. 

Now anything over 60 lbs. will operate the pump, and the faster 
it is run the higher must be the pressure above 60 pounds. 

To find the diameter of water piston when the diameter of 
steam piston, the steam pressure in pounds per square inch, and 
the resistance against the pump piston in pounds per square inch 
are given : — 

Rule*^ — Multiply the area of steam piston in square inches by 
the steam pressure in pounds per square inch, and divide the 
product by the resistance in pounds per square inch on the water 
piston. 

Example* — The resistance against the pump, including fric- 
tion, is 240 pounds per square inch ; the area of steam piston is 
112 square inches, the steam pressure is 60 pounds per square 
inch, what should be the diameter of water piston ? 

Ans. 6 inches. 

112 X 60 

Operation : = 35.65 sqr. ins. Call it 36 sqr. ins. 

240 

Then, ^W = Q>. 

To find the horse power required in a steam pump to feed a 
boiler with a given number of pounds of water per hour against a 
given pressure of steam : — 

Rule* — Multiply the velocity of flow of water in feet per min- 
ute by the total pressure against which the water is pumped in 
pounds per square inch, and divide the product by 33,000, and 
the quotient will be the horse power. 



606 HANDBOOK ON ENGINEERING. 

Example* — What horse power is required to feed a boiler 
with 600 gallons of water per hour against a total resistance of 
112 lbs. per square inch, including the friction in the delivery 
pipe, lift of water in suction pipe, weight of check valve, and 
friction in the pump itself? Ans. 1 H. P. nearly. 

Operation: 600 X 231 = 138,600 cubic inches of water per 

hour. 

138,600 
And, — TTT^ — = 2310 cubic inches of water per minute. 

2310 
And, —r^= 192.5 feet per minute, the velocity of the 

water. 

The total resistance is 112 lbs. per sqr. in. 
Then, 192.5 X 112 = 21560 foot pounds. 

21560 
^^^' 33;000 = -^^^H-^- 

Now add say 50 per cent and we have .653 X .50 ==.3265. 
And, .653 + .3265 = .9795. 

This pump will feed a boiler as shown above, or it will deliver 
600 gallons of water per hour under a head of 258 feet. 

112 
Thus, -^gg=258. 

To find the horse-power of boiler required to furnish steam for 
a pump running at its fullest capacity. 

Rule* — Multiply the number of gallons of water delivered by 
the pumj) in one minute by 8 J. Multiply this product by the 
total height in feet to which the water is to be lifted, measuring 
vertically from the source of supply to the point of delivery, and 
divide the result by 33,000. Add from 50 to 75 per cent to the 
quotient for loss from friction of water in the pipe, friction in 
the pump, waste of steam in the cylinder, and other contingencies, 
and the result will give the horse power of boiler required. 



HANDBOOK ON ENGINEERING. 607 

Example* — What horse-power of boiler is required to run a 
steam pump lifting 800 gallons of water per minute to a height of 
163 ft. from the source of supply? Ans. 50 H. P., nearly. 

Operation i 800 XS^ = 6667 lbs. of water. 

And, 6667 X 163 = 1,086,721 footpounds. 
1,086,721 

^^^' -337000- =^^^-^-' ^^^"^^• 

Then, 33 X .50 = 16.50. 

And, 38 4- 16.5 ==49.5. 

To find the diameter of discharge nozzle for a steam pump, 
when the diameter and stroke of the water piston and the number 
^t strokes per minute are given, and the maximum flow of water 
in feet per minute is given : — 

Rule. — Find the cubic contents of the water cylinder for one 
stroke in cubic feet, and multiply it by the number of strokes per 
minute. Multiply this product by 144 and divide the result by 
the velocity of the water in feet per minute, and the quotient will 
be the area of pump nozzle in square inches. 

Example. — The diameter of water cylinder is 10 inches, and 
the stroke of piston is 12 inches, and the speed is 50 strokes per 
minute. The velocity of water required is 500 feet per minute, 
what should be the diameter of pump discharge nozzle ? 

Ans. 3 J ins., nearly. 

Operation: 10 X 10 X .7854== 78.54 sqr. ins. area of piston. 

And, 78.54 X 12 = 942.48 cubic inches in the cylinder for one 

stroke. 

942.48 
And, -tr-cto = .5454 of a cubic foot for one stroke. 

1 ( Zo 

And, .5454 X 50 = 27.27 cubic feet for 50 strokes per minute. 

27.27 144 , , . 

Then, tttt; = 7.8537 sqr. ms. the area of the nozzle. 

' oOO 



SI. 78 



And, r*^^^'^ = 3.1 ins. the diameter. 
' 7854 



608 HANDBOOK ON ENGINEERING. 

To find the approximate size of suction pipe when its length 
does not exceed 25 ft. and when there are not more than two 
elbows in the same : — 

Rule* — Square the diameter of water cylinder in inches and 
multiply it by the speed of the piston feet in per minute ; divide 
this product by 200, and divide this quotient by .7854 and 
extract the square root, and the result will be the diameter of 
suction pipe, except for very small pipes when it should be made 
larger than the size given by the rule, in order to lessen the friction 
of the moving water. 

Example* — The diameter of water cylinder is 6 ins. , the stroke 
of piston is 12 ins., and the number of strokes per miuute is 60, 
what should be the diameter of suction pipe? Ans. 4 ins- 

Operation; ^X/^^X^^^ 10.8. 

And, 1M,= 13.75. 
.7854 

Then, ^13.75 r= 3.7 ins. There is no pipe of this size made, 
so take 4-inch pipe. 

To find the velocity in feet per minute necessary to discharge 
a given number of gallons of water per minute through a straight 
smooth iron pipe of a given diameter, regardless of friction : — 

Rule* — Reduce the gallons to cubic feet and multiply by 144, 
and divide the product by the area of the pipe in square inches. 

Example* — What should be the velocity of the water to dis- 
charge 100 gallons of water per minute through a 4-inch pipe? 

Ans. 149 ft. per minute. 

. ^ ,. 100X231 ,o u- 4= ^ 

r\ J.' ^N =^13 cubic feet. 

cubic inches placed in a continuous 
= 12.5664 square inches, the area of 



12.5664 



^^^M., 


* 


1 


728 


And, 


13 X 144 r 


= 1872 


line. 








Then, 


4X4 


X 


.7854 = 


pipe. 
And. 


1872 




149. 



HANDBOOK ON ENGINEERING. 609 

To find the velocity in feet per minute of water flowing through 
a pipe of given diameter, when the diameter of water cylinder and 
speed of piston in feet per minute are given : — 

Rule* — Multiply the area of water cylinder in square inches 
by the piston speed in feet per minute, and divide the product bj' 
the area of the pipe in square inches. 

Example* — The diameter of water cylinder is 8 ins., and the 
piston speed is 100 ft. per minute, and the diameter of discharge 
pipe is 4 ins., what is the velocity of the water in the discharge 
pipe? Ans. 400 ft. per minute. 

Operation: 8 X B X .7854 = 50.26 sqr. ins. area of the 
water piston. 

And, 50.26 100 = 5026. 

The area of the pipe is 12.56 sqr. ins. 

^^ 5026 

Then, =400. 

12.56 

To find the number of gallons of water discharged per minute 
through a circular orifice under a given head : — 

Rule* — Find the velocity of discharge in feet per second and 
multiply it by 60, then multiply this product by the area of the 
orifice in square feet, and multiply this last product by 7.48, and 
the result will be the gallons discharged per minute. 

Example. — How many gallons of water will be discharged per 
minute through an orifice 4 inches in diameter under a head of 81 
feet? Ans. 2829.7 galls. 

Operation: V^= ^- ^^^' ^ X 8.025 = 72.225 feet per 
second, the velocity of discharge. The factor 8.025 is a con- 
stant for any head, and is found thusly : — 



V2 X32.2 =8.025. 

Or, the velocity of discharge may be found in this manner : — 
V2 X 32.2 X 81 = 72.22 feet per second, that is, the veloc- 
ity in feet per second equals the square root of the acceleration 



8 10 HANDBOOK ON ENGINEERING. 

due to gravity multiplied into the head in feet. Continuing the 
operation, we have : — 

72.225 X 60 z:^ 4333.5 feet per minute. 

And, 4 X 4 X .7854 = 12.5664 sqr. ins. area of orifice. 

And, — '. = .0873 of a square foot, the area of orifice, 

144 

also. 

Then, 4333.5 X .0873 = 378.3 cubic feet. 

And, 378.3 X 7.48 = 2829.7 galls. 

Note. — With a ring orifice only 64 per cent of the above 
amount of water would be discharged, and with a funnel-shaped 
orifice only 82 per cent. 

To find the number of gallons of water discharged per minute 
under a given pressure in pounds per square inch : — 

Rule. — Divide the given pressure in pounds per square inch 
by .433 in order to get the head in feet, and then proceed accord- 
ing to the foregoing rule. 

Example* — ■ How many gallons of water will be discharged per 
minute through an orifice one square inch in area, under a pres- 
sure of 35.073 lbs. per square inch? Ans. 81 galls, per minute. 

35.073 
Operation: — 4W~=^1 ft., head equivalent to the given 

pressure. 

And, V2X32.2 X81 = 72.225 ft. per second the velocity. 

And, 72.225 X 60 = 4333.5. 

Also, rj-r = .00694 of a square foot, equals the area of the 

orifice. 

And, 4332.5 X .00694 = 30.07449. 
And, 30.07449 X 7.48 = 224.9 galls. 
Then, deducting 64 per cent, we have: — ' 
224.9 X .64= 143.9. 
And, 224.9 — 143. y =81. 



HANDBOOK ON ENGINEERING. 611 

To find the area of orifice in square ins. necessary to discharge 
a given number of gallons of water per minute under a given 
head in feet : — 

Rule. — Divide the number of gallons by the constant number 
15.729 multiplied into the square root of the head, and the result 
will be the area of orifice in square inches. 

Example* — What must be the area of orifice to discharge 
1778.5 gallons of water per minute under a head of 81 feet? 

Ans, 12.56 sqr. ins. 

Operation; V^ = 9. 

And, 9 X 15.729 = 141.6. 

1778.5 
Then, —-pj-^ = 12.56. 
' 141.6 

To find how many gallons of water will flow through a straight 
smooth iron pipe in one minute under a given pressure in pounds 
per square inch, or head in feet : — 

Rule* — Multiply the inside diameter of the pipe in feet by the 
head in feet, and divide the product by the length of pipe in feet. 
Extract the square root of the quotient and multiply it by 48, 
and the product will be the velocity of flow in feet per second. 
Multiply this result by 12 to reduce it to inches, and by 60 for 
the flow per minute, and multiply again by the area of the pipe in 
square inches, and divide by 231 for the gallons discharged^per 
minute. 

Example* — How many gallons of water will be discharged per 
minute through a 4-inch pipe 2000 feet long, under a head of 92 
feet? Ans. 230 galls, per minute. 

Operation : 4 ins. = .33 of a foot. 

And, 92 X .33 = 30.36. 

30.36 
^^^' 2000" = '^^^' 



612 HANDBOOK ON ENGINEERING. 

And, V^015 =.1225. 

Then, .1225 X 48 X 12 = 70.56 ins. per second. 

And, 70.56 X 60 =4233.60 ins. per minute. 

Then, 4 X 4 X .7854 = 12.56 sqr. ins. the area of the pipe. 

And, 4233.60 X 12.56 =53174.016 cubic ins. 

53174.016 
Then, — ^si = 230.2. 

Example* — Assume two wells A and B with their mouths on 
a level. Well A is 26 ft. deep, and well B is 40 ft. deep. Well 
A is fed by natural springs and has a depth of water of 5 feet. 
The distance between the wells is 600 feet. How many gallons 
of water will a 1 inch pipe, laid perfectly straight and level, 
syphon over in one minute providing well B is always pumped 
dry, and that the pipe extends into well ^26 feet, and into well 
B 38 feet, using bends instead of elbows? 

Ans. 4 galls, per minute. 

Operation* — The head equals 38 feet. 
The diameter of the pipe equals .0833 foot. 
Then, 600 + 38 + 26 = 664 ft. total length of pipe. 
And, 38 X .0833 = 3.1654. 

3.1654 
And, -gg-^ = .0047. 

And, V.0047 = .068. 

Then, .068 X 48 = 3.264 ft. velocity per second. 

And, 3.264 X 60 = 195.840 ft. velocity per min. 

The area of pipe equals .7854 sqr. inch. 

Then, 195.840 .7854 = 153.8127. 

And, 153.8127X7.48 = 1150.52. 

1150.52 
And, — Yli — = ^ nearly, gallons. 



HANDBOOK ON ENGINEERING. 613 

Deducting 50 per cent on account of 2 bends and friction, we 
have 4 gallons per minute syphoned over. 

To find the head in feet due to friction in a pipe running 
full: — 

Rttle* — Multiply the length of the pipe in feet by the square 
of the number of gallons per minute, and divide the product by 
1,000 times the 5th power of the diameter of the pipe in inches. 
The quotient less 10 per cent is the head in feet necessary to over- 
come the friction. 

Note. — The head is the vertical distance from the surface of 
the water in the tank or reservoir, to the center of gravity of the 
lower end of the pipe, when the discharge is into the air, or, to 
the level surface of the lower reservoir when the discharge is under 
the water. 

Example^ — A 2-inch pipe 100 feet long and running full, 
discharges 50 gallons of water per minute, what is the head in 
feet due to friction? Ans. 7.029 feet. 

Operation: 2 X 2 X 2 X 2 X 2 = 32 = the 5th power of the 
diameter of the pipe. 

And, 50 X 50 = 2500. 
And, 2500 X 100 = 250,000. 
Also, 32 X 1,000 = 32,000. 

250,000 
T^^^' ^2:000- -^^-^l- 

And, 7.81 less 10 percent of itself equals 7.029. 
The resistance to the flow of water in pounds per square inch, 
due to friction, is found by dividing the friction head by 2.3. 

7.029 
Thus, Y^=^^'^^^^^' 

To find the size of pump required to feed a boiler of a given 
capacity : — 



614 HANDBOOK ON ENGINEERING. 

Rule. — Multiply the number of pounds of water evaporated 
per pound of coal by the number of pounds of coal burned per 
sqr. foot of grate surface per hour, and multiply this product by 
the number of square feet of grate surface in the boiler furnace. 
This will give the number of pounds of water evaporated by the 
boiler in one hour. Divide this by 60 to find the evaporation per 
minute, and divide again by 8^ in order to get the evaporation in 
gallons per minute ; add from 10 to 15 per cent to the last result 
for leakage and other contingencies, and select a pump that will 
deliver the gross number of gallons of water per minute at any 
speed that may be desired, usually taken, however, at 100 feet 
per minute. 

Example. — What should be the dimensions of the water end 
of a steam pump, and what should be the speed of piston to sup- 
ply a boiler having a grate surface of 20 square feet, and burning 
15 pounds of coal per square foot of grate, and evaporating 9 
pounds of water per pound of coal per hour ? 

Operation: 20 X 15 X 9 =2700 pounds of water evapo- 
rated per hour. 

And, = 45 lbs. of water evaporated per minute. 

And, — = 5.4 ffalls. per minute. 
' 8J 

Then, 5.4 plus 10 per cent of itself, equals 6 galls, nearly per 

per minute. 

, Referring to a pump maker's catalogue we find that a single 

pump 3J" X 2|" X 5", making 90 strokes per minute, will do 

the work, or, a duplex pump 3" X 2" X 3", making 100 strokes 

per minute will do the work equally as well. Again, adding 10 

per cent to the pounds of water evaporated per minute we have, 

45 + 4.5 = 49.5 pounds. And, 49.5 X 27.71 = 1371.64 cubic 

inches displacement in the water cylinder per minute, and at 90 

strokes per minute we have 15.24 cubic inches displacement per 

stroke. 



HANDBOOK ON ENGINEERING. 615 

Thus, '- = 15.24 which is all that is required for our 

90 ^ 

boiler. 

Now, taking the above single pump we have: 2.25 X 2.25 X 
.7854 X 5 = 19.8 cubic inches displacement per stroke. And, 
taking the duplex pump we have: 2 X 2 X .7854 X 3 X 2 = 
18.8 cubic ins. displacement for each double stroke of the piston, 
or, plunger, showing that either pump is of ample capacity to 
feed the boiler at a fair piston speed. 

To find the duty of a pumping engine when the number of 
pounds of coal burned, the number of gallons of water pumped, 
the pressure in pounds per square inch against which the pump 
piston works, and the height of suction are given : — 

Rule^ — Find the head in feet against which the pump works, 
by multiplying the pressure by 2.3, add the suction in feet 
to this head in order to get the total head. Multiply the 
gallons of water by 8J to get the pounds of water deliv- 
ered. Then multiply the total number of pounds of water 
by the head in feet, and divide the product by the number of 
pounds of coal divided by 100, and the result will give the duty 
in foot pounds. The duty of a pumping engine is the number of 
pounds of water raised one foot high for each 100 pounds of coal 
burned. 

Example* — What is the duty of an engine pumping 2,890,000 
gallons of water in 12 hours against a pressure of 30 pounds per 
sqr. inch, the suction being 12 feet, and coal burned 24,470 
pounds? Ans. 8,070,426 foot pounds. 

Operation: 30 X 2.3 = 70 nearly the head in feet. 

And, 2,890,000 X 81- r= 24,083,333 pounds of water. 

Also, 70 + 12 =:-- 82 ft. total lift of water. 

And, 24,083,333 X 82 = 1,974,833,306 lbs. of water lifted 
one foot high in 12 hours. 

Then, 2M!? = 244.7. 
100 



616 HANDBOOK ON ENGINEERING. 

1,974,833,806 ^^^^^ 
244.7 
To find the horse power of a pumping engine : — 
Rule^ — Divide the number of pounds of water raised one foot 
high in one minute by 33,000. 

Example* — What is the H. P. of the pumping engine given 
in the above example? Ans. 83.11 H. P. 

Operation: 12 X 60 = 720 minutes. 

And, l^Q^^^Q^^^^Q^ ^ 2,742,824 lbs. of water raised one foot 
720 

high in one minute « 

Then, MlM^i^ 83.11. 
33,000 

To find the capacity of a pump to feed a boiler it is necessary 
to know how much water the boiler is capable of evaporating per 
minute or per hour. Each horse power of boiler capacity corre- 
sponds to an evaporation of thirty pounds of water per hour. It 
is good practice to operate a pump slowly and continuously, and 
for this reason the pump running at its normal speed should be 
capable of supplying about twice as much water as the boiler 
evaporates under usual conditions. 

To find the diameter of water cylinder to deliver a certain num- 
ber of gallons of water per minute, when the stroke of the piston 
and the number of strokes per minute are given : — 

Rule. — Multiply the number of gallons by 231, and divide the 
product by the stroke of the piston, and divide this quotient by 
the number of strokes per minute, and divide this last quotient 
by .7854, then extract the square root of the result for the 
diameter of the water piston. 

Example* — A battery of boilers evaporate 100,000 pounds of 
water in one hour, what should be the diameter of water cylinder 
to supply this battery, the stroke of piston being 12 inches and 
making 100 strokes per minute? Ans. 7 inches. 



HANDBOOK ON ENGINEERING. 617 

100,000 
Operation :^ — -^0 — ^=1(366| pounds of water evaporated in 

one minute. 

1666-f 
And, r,^ ===200 galls, evaporated in one minute. Then 

following the above rule we have : ■ — 

200 X 231 =46200. 

46200 
And, ^^ =3850. 

3850 
And, -j^ =38.5. 

38.5 
•^^^' 77854 =^^- 

Then, i/49 =7" the required diameter. 

To determine the ,H. P. of boiler a steam pump of given 
dimensions will supply when the number of strokes per minute 
are given : — 

Rulc» — Multiply the area of the piston is square inches by the 
stroke of piston in inches, and this product divided by 231 will 
give the gallons per stroke. Multiply this quotient by the num- 
ber of strokes per minute for the number of gallons per minute, 
and by 60 for the number of gallons per hour. Multiply this 
product by 8i to find the number of pounds of water per hour 
delivered by the pump, and divide this product by 30 for the 
H. P. of boiler the pump will supply. This rule is based upon the 
assumption that the full capacity of the water cylinder is deliv- 
ered at each stroke, no allowance being made for slippage, leak- 
age, or short strokes. 

Example. — = The water piston of a steam pump is 6 inches in 
diameter and has a stroke of 12 inches, making 100 strokes per 
minute, what H. P. of boiler will the pump supply? 

Ans. 2448 H. P. 



G18 HANDBOOK ON ENGINEERING. 

Operation: 6 X 6 X .7854 = 28.2744 sqr. ins. area of 
piston . 

And, 28.2744 X 12 = 339.2928 cubic inches for one stroke. 

339.2928 
And, — ^:r- — =-• 1.4688 galls, per stroke. 

And, 1.4688 X 100 = 146.88 galls, per minute. 

And, 146.88 X 60 = 8812.8 galls, per hour. 

And, 8812.8 X 8 1 = 73,440 pounds of water per hour. 

73440 
Then, ^ = 2448 H. P. of boilers. 

Watt allowed one cubic foot (62 J lbs.) of water per H. P. per 
hour. Then taking this allowance instead of 30 as above, we 

73440 
would have, ^^ . =^ 1175 H. P. of boilers which the above pump 

would be suitable for, and which could be run very slowly, thus 
prolonging the life of the pump. 



HANDBOOK ON ENGINEERING. 



619 



CHAPTER XXI. 
MECHANICAL REFRIGERATION. 

About the first thing asked by persons who are becoming 
interested in the subject of refrigerating and ice-making is, " Tell 
me how the thing is done ? " 

Mechanical refrigeration, primarily, is produced by the evapo- 
ration of a volatile liquid which will boil at low temperature, and 
by means of a special apparatus the temperature and desired 
amount of refrigeration is placed under control of the operator. 




Elemental Refrigerating Apparatus. 
Fig. 1. 



The simplest form of refrigerating mechanical apparatus 
consists of three principal parts: A, an "evaporator," or, as 
sometimes called, a " congealer," in which the volatile liquid is 
vaporized; 5, a combined suction and compressor pump, which 



620 



HANDBOOK ON ENGINEERING. 



sucks, or proper]}^ speaking, " aspirates " the gas discharged by 
the compressor pumps, and under the combined action of the 
pump pressure and cold condenser, the vapor is here reconverted 
into a liquid, to be again used with congealer. You now see the 
function of the compressor pumps and condensers. 

PRINCIPLES OF OPERATION. 

The action of all refrigerating machines depends upon well- 
defined natural laws that govern in all cases, no matter what type 
of apparatus or machine is used, the principle being the same in 
all ; while processes may slightly vary, the properties of the par- 
ticular agent and manner of its use affecting, of course, the 
efficiency or economic results obtained. 




Fig. 2. — Outline drawing of mechanical compression system 



OPERATION OF APPARATUS. 

(See Fig"* 2*) The ai3paratus being charged with a sufficient 
quantity of pure ammonia hquid, which we will, for simplicity, 
assume to be stored in the lower part of the condenser C, a small 
cock or expansion valve controlling a pipe leading to the congealer 



HANDBOOK ON ENGINEERING. 621 

or brine tank A, is slightly opened, thus allowing the liquid to 
pass in the same office as a tube or flue in steam boiler and having 
precisely the same function, it may be called heating or 
steam -making service. The amount of water capable of being 
boiled into steam in a boiler depends upon the square feet of heat- 
ing surface, temperature of fire and pressure of steam ; and 
the same is true of the capacity of heating surface pre- 
sented by the coils in the evaporator. The heat is transmitted 
through the coils from surrounding substance to the ammonia 
liquid, which is boiled into a vapor the same as water is boiled 
into steam in a steam boiler ; as previously explained, the heat 
thus becomes cooler ; the amount taken up and made negative 
being in proportion to the pounds of liquid ammonia evaporated. 

FUNCTION OF THE PUHP AND CONDENSER. 

The office of the comjjressor, pump and condenser is to re- 
convert the gas after evaporation into a liquid, and make the 
original charge of ammonia available for use in the same appa- 
ratus, over and over again. It will appear to the reader, after 
having carefully followed the text, that the pump and condenser 
might be dispensed with, but these conditions may only be eco- 
nomically realized when the, at present, expensive ammonia 
liquid can be obtained in great quantities and at less cost than 
the process of reconverting the vapor into a liquid by compression 
machinery and condenser on the spot. 

WHAT DOES THE WORK. 

The real index of the amount of cooling work possible is the 
number of pounds of ammonia evaporated between the observed 
range of temperature. To make the above clear, we will add 
that each pound of ammonia during evaporation is capable of 
storing up a certain quantity of heat, and that the simplest forms 



622 HANDBOOK ON ENGINEERING. 

of refrigeratiDg apparatus might consist, as shown by engraving, 
of two parts, to wit : A congealer and a tank of ammonia. In this 
apparatus the ammonia is allowed to escape from the tank into 
the congealer as fast as the coils therein are capable of evapo- 
rating the liquid into a gas. When completely evaporated the 
resulting vajjor is allowed to escape into the atmosphere, which 
means it is wasted, the supply being maintained by furnishing 
fresh tanks of ammonia as fast as contents are exhausted. This 
process, while simple, would be tremendously expensive, costing 
at the rate of about $200 per ton, refrigerating or ice-melting 
capacity. To recover this gas and reconvert to a liquid on the 
spot in a comparatively inexpensive manner, is the object to be 
obtained. 

MECHANICAL COLD EASILY REGULATED. 

This being under the control of the cock or valve leading from 
the condenser (called an expansion valve). As the gas begins to 
form in the evaporator, the compressor pump B is set in motion 
at such a speed as to carry away the gas as fast as formed, which 
is discharged into the condenser under such pressure as will bring- 
about a condensation and restore the gas to the liquid state ; the 
operation being continuous so long as the machinery is kept in 
motion. 

UTILIZING THE COLD. 

To utilize the cold thus produced for refrigerating, two meth- 
ods are in use, the first of which is called the brine system ; the 
second is known to the trade as the direct expansion system, both 
of which I will now proceed to explain at some length. 

BRINE SYSTEM. 

In this method, the ammonia evaj^orating coils are placed in a 
tank which is filled with strong brine made of salt, which is well 
known not to freeze at temperature as low as zero. This is the brine 



HANDBOOK ON ENGINEERING. 623 

tank or congealer A. The evaporating or expansion of the ammo- 
nia in these coils robs the brine of heat, as heretofore explained, 
the process of storing cold in the brine going on continuously and 
being regulated, as required, at the gas expansion valve. To 
practically apply the cold thus manufactured, the chilled brine or 
non-freezing liquid is circulated by means of a pump through 
coils of pipe which are placed on the ceilings or sides of the apart- 
ments to be refrigerated, the process being analogous to heating 
rooms by steam. 

THE BRINE COOLS THE ROOMS. 

The cold brine in its circuit along the pipes becomes warmer 
by reason of taking up the heat of the rooms, and is finally 
returned to the brine tank, where it is again cooled by the ammo- 
nia coils, the operation, of course, being a continuous one. 

DIRECT EXPANSION SYSTEM. 

By this method, the expansion or evaporating coils are not put 
in brine tanks, but are placed in the room to be refrigerated, and 
the ammonia is evaporated in the coils by coming in direct con- 
tact with the air in the room to be refrigerated, no evaporating 
tank being used. 

RATING OF THE MACHINE IN TONS CAPACITY. 

For the information of the unskilled reader, 1 will state that 
machines are susceptible of two ratings; that is, either their 
capacity is given in tons of ice they will produce in one day (24 
hours), called ice-making capacity ; or they are rated equal to the 
cooling work done by one ton of ice-making per day (24 hours), 
called refrigerating capacity. 

DIFFERENCE IN THESE RATINGS. 
Ordinarily the ice-making capacity is taken at about one-half 
of the refrigerating capacity, but this is only approximate, and 



624 



HANDBOOK ON ENGINEERING. 



the tons of ice a refrigerating machine will make depend upon the 
initial temperature of the water to be frozen. 

UNIT OF CAPACITY. 

The unit of capacity is one ton of ice made from water at 32° 
Fahr., into ice at 32°, per day, which is equal to 284,000 lbs. of 
water cooled one degree, or 284,000 heat units, and is the tannage 
basis for refrigerating capacity as well as ice made from water 
at 32°. 

THE PREPARATION OF BRINE. 




Fip-. 1. 



There are two methods in general use, which I will exj^lain. 
Fig. 1 shows one of the methods, which consists of allowing 
water to percolate through a body of salt. 

Take ^ large water-tight barrel or cask, and fit a false bottom 



HANDBOOK ON ENGINEERING. {y2i) 

or wooden grating six or eight inches above the bottom ; this can 
be made of strips of wood about an inch square, and placed not 
over one-half inch apart. This false bottom should be supported 
by two strips of boards, each six inches in width, placed on edge 
and nailed to the bottom. These boards should have several holes 
bored near their bottoms to permit a free passage of water. The 
water inlet should be below the false bottom. A single thickness 
of burlap should be stretched across the top of the false bottom 
and tacked to sides of barrel. The outlet pipe for the brine 
should be four or five inches below the top of the barrel. The 
water is supplied at the bottom from a convenient hose or faucet. 
The supply pipe should be of about IJ in. diameter ; and the 
outlet pipe about IJ in. diameter. If it is necessary to make 
brine faster than can be accomplished with one barrel, fit up two 
or more extra barrels. To make brine, fill the barrel above the 
false bottom with salt and turn on the water. The salt dissolvCg 
rapidly and more must be shoveled in on top. The barrel must 
be kept full of salt or the brine will not be of full strength. No 
stirring is necessary. Keep skimming off all waste matter rising 
to the top. The brine outlet should be provided with a strainer 
of some kind to prevent chips, etc., from running out with the 
brine. Brine should not be made any stronger than is necessary 
to prevent it from freezing. 

Fig. 2 is the other method of brine-making.' This method is 
a water-tight box, say four feet wide, 8 feet long and 2 feet high, 
with perforated false bottom and compartment at end. Locate 
the brine-maker at a point above the brine tank.C onnect the 
space under the false bottom with your water supply, extending 
the pipe lengthwise of the box, being perforated at each side to 
insure an equal distribution of water over the entire bottom surface ; 
use a valve in water supply pipe. Near the top of the brine- 
maker, at end compartment, put in an overflow with large strainer 
to keep back the dirt and salt, and connect with this a pipe, say three 



626 



HANDBOOK ON ENGINEERING. 



inches in diameter, with salt catcher at bottom, leading into the 
brine tank. Use a hoe or shovel to stir the contents. When all is 
ready, j^artly fill the box with water, dump the salt from the bags 

<Nv,^ Salt Gauge 




Complete Brine Mixing Arrangement . 
Fig. 2. 

on the floor alongside and shovel into brine-maker or dump direct 
from the bags into the brine-maker as fast as it will dis- 
solve. Regulate the water supply to always insure the brine 
being of the right strength as it runs into the brine tank. This 
point must be carefully noticed. Filling the brine tank with 
water and attempting to dissolve the salt water directly therein is 
not satisfactory, as quantities of salt settle on the tank bottom 
coils, forming a hard cake. It is a good plan, when desired to 
strengthen the brine, to suspend bags of salt in the tank, the salt 
dissolving from the bags as fast as required ; or the return brine 
from the pumps may be allowed to circulate through the brine- 
maker, keeping same supplied with salt. 

INSULATION OF BUILDINGS. 

The insulation of buildings used for the preservation and 
storage of substances subjected to mechanical refrigeration, is a 



HANDBOOK ON ENGINEERING. 



627 



IN5ULATING BUILDINGS AND COLD STORAGE ROOnS. 




14. inch Brick 
4 " Air Space 
9 'f Brick 

Cement Wash 

Pitched 

2"x 3"Studding 

Tar Paper 

■1"T&G. Board 

2"x 4"Studding- 

-V'T k G. Board 

>Tar' Paper 

-r'T.&:G. Board 




■14 Brick , 
4" Pitch &■ Ashes. 
4"' Brick 




^^^ffgf^^^gi_^g ^ 



•36" Brick Wall 
•Pitch 

•T'Sheathing 
•4"Air Space 
2"x 4"Studding 
•T'Sheathing - 
Mineral Wool 

. 2"x 4"Studding 

^"Sheathing 



Various Approved Methods. 



628 HANDBOOK ON ENGINEERING. 

matter of vital importance, when viewed from an economic stand- 
point. It is true that by employment of a large surplus of 
refrigerating power, poor insulation with its entailed great loss 
of negative heat is wastefully overcome, and a certain amount of 
cooling work can be accomplished ; but this is a bad way to reacli 
a result ; it is like pumping out a leaky ship and keeping ever- 
lastingly at it, when the best way is to stop the leak and be done 
with the pumping — it is a preventable loss. Poor insulation is 
like paying interest on borrowed capital, which is earning nothing 
for the borrower, a never-ceasing and useless drain upon the 
machinery and pocket-book of the user. 

PERFECT INSULATION. 

Perfect insulation is when there is absolutely no transfer of 
heat through the walls of a building ; but this is scarcely pos- 
sible. If it were, once cooling of the contents of a room would 
suffice ; for there being no loss, they w^ould continue at the same 
temperature for an indefinite period. If all articles placed in the 
room thereafter were previously cooled to the temperature of the 
room before placing therein, no work n^ed be done thereafter in 
the room itself. A large percentage of the actual work of a 
refrigerating machine is required to make u]^ for transfer of heat 
through the walls, floors and ceilings occasioned by improper 
insulation, and the amount may be experimentally determined 
by i)roper instruments. Owing to difference in construction, 
exposure and insulation of building, you will find a great dif- 
ference in economy of performance and work done by the 
same machine in use by different parties in the same line of 
business ; and what a given machine and apparatus will do in 
one place is no certain guide for another place somewhat sim-' 
ilar ; the insulation, exposure, and method of handhng the 
business are mainh resoonsible for the difference. 



HANDBOOK ON ENGINEERING. 



629 



As shown by the engraving, screw into tlie ammonia flask a 
piece of bent one-quarter inch pipe, which will allow a small bot- 
tle to be placed so as to receive the discharge from it. This test 
bottle should be of thin glass with wide neck, so that quarter-inch 
pipe can pass readily into it, and of about 200 centimeters capac- 
ity. Put the wrench on the valve and tap it gently with a ham- 
mer. Fill the bottle about one-third full and throw sample out 
in order to purge valve, pipe and bottle. Quickly wipe off mois- 
ture that has accumulated on the pipe, replace the bottle and open 

CLASS^TUBE 

AUBBER' 




Testing for Water by Evaporation. 



valve gently, filling the bottle about half full. This last operation 
should not occupy more than one minute. Remove the bottle at 
once and insert in its neck a stopper with a vent hole for the 
escape of the gas. A rubber stopper with a glass tube in it is 
the best, but a rough wooden stopper, loosely put in, will answer 
the purpose. Procure a piece of solid iron that should weigh not 
less than eight or ten pounds, pour a little water on this and place 
the bottle on the wet place. The ammonia will at once begin to 
boil, and in warm weather will soon evaporate. If any residuum, 
pour it out gently, counting the drops carefully. Eighteen drops 
are about equal to one cubic centimeter, and if the sample taken 



630 



HANDBOOK ON ENGINEERING. 



amounted to 100 cubic centimeters, you can readily approximate 
the percentage of the liquid remaining. 




S€ction,al View of lo-ton Refrigerating Machine, regular pat- 
tern. Frick Company's Eclipse Refrigerating Machine, 
with Placer Slide-Valve Throttling Machine. 



LUBRICATION OF REFRIGERATING MACHINERY. 

It is well to speak of this, for the reason that it is an important 
subject ; and some users of machinery think that a cheap, low 

29 



HANDBOOK ON ENGINEERING. 631 

grade of oil is really the cheapest. To disabuse their minds of 
this idea and suggest the necessity of high grade oils, both on the 
score of economy and to keep the machinery at all times in 
efficient running order, is the object of this article. First-class 
refrigerating machinery calls for the use of at least three different 
kinds of oil, Nos. 1, 2 and 3, each of high grade: — 

No* \* For use in the steam cylinder, and is known in the trade 
as cylinder oil. This ranges in price from 50c. to $1 per gallon. 
Good cylinder oil should be free from grit, not gum up the valves 
and cylinder, should not evaj^orate quickly on being subjected to 
heat of the steam, and when cylinder head is removed, a good 
test is to notice the appearance of the wearing surfaces ; they 
should be well coated with lubricant which, upon application of 
clean waste, will not show a gummy deposit or blacken. Use this 
oil in a sight feed lubricator with regular feed, drop by drop. 

No» 2* For use of all bearing and wearing surfaces of machine 
proper — an oil that will not gum, not too limpid, with good 
body, free from grit or acid and of good wearing quality, flowing 
freely from the oil cups at a fine adjustment without clogging, 
and a heavier grade should be used for lubricating the larger 
bearings. 

No* 3* For use in compressor pumps. This oil should be what 
is called a cold test, or zero oil, of best quality. 

Best paraffine oil is sometimes used ; as also a clear West Vir- 
ginia crude oil. This oil, when subjected to a low temperature, 
should not freeze. 

EFFECTS OF AMMONIA ON PIPES. 

Ammonia lias* no chemical effect upon iron ; a tank, pipe or 
stop-cock may be in constant contact with ammonia for an in- 
definite time and no action will be apparent. The only protec- 
tion, therefore, that ammonia-expanding pipes require is from 
corrosion on the outer surface. As long as the pipes are covered 



632 HANDBOOK ON ENGINEEKING. 

with suow or ice, corrosion does not occur ; the coating of ice 
thoroughly protects them from the oxidizing effect of the atmos- 
phere ; but alternate freezing and thawing requires protected sur- 
faces, which are best obtained by applying a coat of paint every 
season. 

Expansion coils having to withstand but a maximum working- 
pressure of thirty pounds per square inch, are constructed with 
such absolute security, in whole and in detail, as to make them 
one of the most perfect pipe constructions on a large scale ever 
applied in practice. 




Position of Tank to be Emptied., 

TO CHARGE THE SYSTEM WITH AMMONIA. 

Position of the tank should be as shown, the outlet valve 
pointing upwards and the other end of the tank raised 12" to 15". 
The connection between the outlet valve of the tank and the 
inlet cock of the system should be a |" pipe. In charging, open 
valve of the tank cautiously to test connection ; if this is tight, 
open valve fully; start machine and run slowly till tank is empty. 
The tank is nearly empty when frost begins to appear on it ; run 
the machine till suction gauge reaches atmospheric pressure. If 
it holds at this pressure when machine is stopped, the tank is 
empty ; if not, start up again. In disconnecting, close the valve 
on the tank first, the inlet cock of the system. Weigh tank 



HANDBOOK ON ENGINEERING. 633 

before and after emptying ; each standard tank contains from 100 
to 110i3ounds of ammonia. 

PROCESS OF MECHANICAL REFRIGERATION. 

The process of mechanical refrigeration is simply that of 
removing heat, and mechanism is necessary, because the rooms 
and articles from which the heat is to be removed are already as 
cold, or colder than their surroundings, and consequently, the 
natural tendency is for the heat to flow into them instead of out of 
them. The fact that a body is already cold does not prevent the 
removal of more heat from it and making it still colder. The term 
cold describes a sensation and not a physical property of matter ; 
the coldest bodies we commonly meet with are still possessed of a 
large quantity of heat, part of which, at least, can be abstracted 
by suitable means. The only means by which heat can be 
removed from a body is to bring in contact with it a body colder 
than itself. This is the function that ammonia performs in 
mechanical refrigeration. It is so manipulated as to become 
colder than the body we wish to cool. The heat thus abstracted 
by it is got rid of b}^ such further manipulation that (while still 
retaining the heat it has absorbed) it will be hotter than ordi- 
nary cold water, and therefore, part with its heat to it. Ammonia 
thus acts like a sponge. It sops up the heat in one place and 
parts with it in another, the same ammonia constantly going 
backward and forward to fetch and discharge more heat. The 
complete cycle of operation comprises three parts : — 

1st. A compression side^ in which the gas is compressed. 

2d. ^1 condensing side, generally consisting of coils of pipe, 
in which the compressed gas circulates, parts with its heat and 
liquefies. 

3d. An expansion side, consisting also of coils of pipe, 
in which the liquefied gas re-expands into a gas, absorbs heat, 
and performs the refrigerating work. 



()34 HANDBOOK ON ENGINEERING. 

In order to render the operating continuous, these three sides 
or parts are connected together, the gas passing through them in 
the order named. The liquefied gas is allowed to flow into the 
expansion or evaporating coils, where it vaporizes and expands 
under a pressure varying from 10 to 30 pounds above that of the 
atmosphere, when ammonia is the agent in use. The gas then 
passes into the compressor, is compressed and forced into the 
condensers, where a pressure from 125 to 175 pounds per square 
inch usually exists ; here liquefaction takes place and the re- 
sulting liquefied gas is allowed to flow to a stop-cock having a 
minute opening, which separates the compression from the expan- 
sion side of the plant. The expansion side consists of coils of 
pipe similar to those of the condensing side, but used for the 
reverse operation, which is the absorption of heat by the vapor- 
ization of liquefied gas instead of the expulsion of heat from it, 
as in the former operation. Heat is conducted through the ex- 
pansion or cooling coils to, and is absorbed by, the vaporizing 
and expanding liquefied gas within such coils, for the reason that 
they are connected to the suction or low pressure side of the 
apparatus from which the compressors are continually drawing 
the gas and thereby reducing the pressure in said coils, as already 
stated, to a pressure of 10 to 30 pounds above the atmosphere; 
it being kept in mind that liquefied ammonia in again assuming 
a gaseous condition, has the power or capacity of reabsorbing, 
upon its expansion, a large quantity of heat. The liquefied gas 
entering these coils through the minute openings of the stop-cock, 
above referred to, is relieved of a pressure of 125 to 175 pounds, 
the amount requisite to maintain it in a liquid condition, when it 
begins to boil, and in so doing passes into the gaseous state. To 
do this it must have heat, which can be supplied only from the 
substance surrounding the pipes, such as air, brine, wort, etc. 
As a natural result the surrounding substances are reduced in 
temperature, or cooled. It is apparent from the foregoing that 



HANDBOOK ON ENGINEERING. 



(335 




The above is a Sectional Cut of the "Eclipse" Compressor. 



636 HANDBOOK ON ENGINEERING. 

if the expansion coils are placed in an insulated room, that room 
will be refrigerated ; also, if brine or wort is brought in contact 
with the surface of the coils, they also will be reduced in tem- 
perature ; and that brine so cooled can be used to refrigerate an 
insulated room by simply forcing it to circulate through pipes 
or gutters suspended in the same. Either of the above methods 
can be applied to the refrigeration of breweries, packing-houses, 
etc., and for the manufacture of ice, the same gas being used 
over and over again to perform the same cycle of operations. 

THE COMPRESSOR PUMPS. 

The most important feature of a refrigerating machine is the 
compressor pump. To some, the highest efficiency of perform- 
ance (other things being equal, such as proper application and 
proportion of the steam engine dividing the same, with the lowest 
obtainable loss of friction in transmission of power to the 
pump) is the pump which receives the fullest charge of gas 
and most perfectly expels the same ; this is the most efficient 
and will do the most work. 

THE DE LA VERQNE HORIZONTAL COMPRESSOR. 

This compressor is of an entirely new design, embodying all 
the improvements suggested by experience up to date, and having, 
moreover, many original features. 

Particular attention is directed to the following points : — 

The valves are all in the body of the compressor. 

No pipe joints have to be broken to remove the valves or the 
cages. 

The delivery valves are so placed as to allow a free and early 
draining of the cylinder, if liquid should be present. 

The valves are so arranged and provided with such safety 



HANDBOOK ON ENGINEERING. 



637 



devices as to render it impossible for them to get inside the cylin- 
der under any circumstances. 

The stuff ingf-box is effectually sealed, without producing 
undue friction. 





Flat Pipe Coils Suspended from Ceiling on Iron Floors — Beams 
for Storage and Fermenting Rooms. 



DIAGRAM OF DE LA VERQNE SYSTEM. 

The diagram on page 638 is seen to be extremely simple in 
conception ; ammonia, gas and oil are received into the com- 



638 



HANDBOOK OX ENGINEERING. 



pressor, from which they are discharged together into the cooler. 
The cooled oil drops into the first tank while the gas continues 
into the condenser, where it is liquefied and collects in the second 
tank. The liquid ammonia is taken off from a point near the top 
of the second tank. If a little oil is taken over from the conden- 
ser it is conveyed by a pipe, as showni, to a point near the bottom 




of the second tank, where it remains, since it is heavier than 
liquid ammonia, and cannot rise to get into the liquid pipe of the 
ammonia supply. The liquid ammonia is passed through the 
expansion cock into the expansion coil, where it boils into vapor 
which is drawn off into the compressor to pass around again in 
the order above described. 



RATING MACHINES FOR ICE=nAKING. 

Reffig-erating machines are rated by the effect they produce 
equivalent to the melting of a corresponding amount of ice. Now 
the melting of one pound of ice is equivalent to the absorbing of 



HANDBOOK ON ENGINEERING. 



639 




Q 



b£ 



03 



640 



HANDBOOK ON ENGINEERING. 



o 

o 






O 

o 
B 




HANDBOOK ON ENGINEERING. 



641 



142 units of heat. In making ice from water, we have, however, 
to remove more than 142 units. We have first of all to reduce 
the water to 32° before we are ready to produce ice. If the water 
is at 82° this means the removal 50 heat units. Moreover, we 
cannot make ice with economy without going to a temperature 
much lower than 32°. The ice when formed may have a temper- 
ature of 18°, and the specific heat of ice being 0.5 this means the 




M^ 



Diagram of the De La Vercne Ice-Making System, 

The above cut shows, in diagrammatic form, the general outline of 
the process of ice-making with cans. 



removal of 7 more heat units. In other words, we have to 
remove 199 heat units instead of 142 to produce a ton of ice. 
Thus a 200-ton machine which would easily produce a refrigerat- 
ing effect equal to the melting of 200 tons of ice would only pro- 
duce 142 tons of actual ice. This proportion' is still further 
reduced by the inevitable losses attending the use of large freezing- 
tanks and the handling of the ice. 



642 



HANDBOOK ON ENGINEERING. 




HANDBOOK ON ENGINEERING. 643 

COnPLETE CYCLE STANDARD DE LA VERGNE VERTICAL 
MACHINE. 

The cut on preceding page shows the engme-room connections 
for the double acting vertical compressor complete with Corliss 
engine. The course of the gas can be very readily followed : 
After being discharged from the compressor it rises to the /ore 
cooler, where the oil is cooled and deposited in thepressitre tank. 
The ammonia gas goes on to the condenser^ which it enters at the 
bottom. As fast as the liquid ammonia collects in the condenser, 
it is drawn off at different levels in the manner already described 
in connection with the condensers. From the storage tank it falls 
into the separating tank, where any remaining oil is trapped, and 
the anhydrous ammonia passes into the rooms to be cooled byway 
of the main liquid pipe. 

The sectional view on following page, represents one of the 
De La Vergne Double Acting Vertical Compressors, as arranged 
for use with oil, as a sealing, lubricating and cooling agent. Two 
passages, marked " suction" and" discharge," respectively, con- 
nect the compressor with the pipe system. On the up stroke, gas 
flows through the lower suction valve into the space behind the 
moving piston, while the gas above the piston, after being com- 
pressed to the condenser pressure, is discharged through the up- 
per valves (in the loose head) into the discharge passage. On 
the down stroke, gas flows into the cylinder through the upper 
suction valves, and the gas below the piston is compressed and 
passes through the lower discharge valves into the discharge pas- 
sage. The piston in its downward course, closes successively the 
openings of these two discharge valves. When the lower is 
closed, however, the upper one communicates with the chamber 
in the piston, and the gas and oil still remaining below the piston 
are discharged through the valves into the chamber and out by 
f-he upper discharge valve, The oil being injected (iirectlj mtq 



644: 



HANDBOOK ON ENGINEERING. 




HANDBOOK ON ENGINEERING. 



645 



the compressor iifter the compression of the full cylinder of gas 
has commenced, does not reduce the capacity of the machine. 




The above is a cut of the De La A^ergne Double Acting Com- 
pressor, driven by a Corliss Engine. Both the compressor and 
engine cylinder, affording an opportunity of observing the relative 
positions of the pistons in each. 

The oil for " cooling, sealing and lubricating " is brought to 
the compressor by the pipe running along the back of the " A " 
frame. The pipe marked "By-pass" is used when any portion 
of the pipe system in the engine house is to be independently 
exhausted of gas. 



(i46 HANDBOOK ON ENGINEERING. 



CHAPTER XXII. 

SOHE PRACTICAL QUESTIONS USUALLY ASKED OF EN= 
QINEERS WHEN APPLYING FOR LICENSE. 

Q. If you were called on to take charge of a plant, what would 
be your first duty? A. To ascertain the exact condition of the 
boiler and all its attachments (safety-valve, steam-gauge, pump, 
injector) and engine. 

Q. How often would you blow off and clean your boilers if 
you had ordinary water to use? A. Twice a month. 

Q. What steam pressure will be allowed on a boiler 50" diam- 
eter, I" thick, 60,000 T. S. J of tensile strength factor of safety? 
A. One-sixth of tensile strength of plate, multiplied by thick- 
ness of plate, divided by one-half of the diameter of boiler, gives 
safe working pressure. 

Q. How much heating surface is allowed per horse-power by 
builders of boilers ? A. 12 to 15 feet for tubular and flue boilers. 

Q. How do you estimate the strength of a boiler? A. By its 
diameter and thickness of metal. 

Q. Which is the best, single or double riveting? A. Double 
riveting is from 16 to 20 per cent stronger than single. 

Q. How much grate surface do boiler -makers allow per horse- 
power? A. About f of a square foot. 

Q. Of what use is a mud drum on a boiler, if any? A. For 
collecting all the sediment of a boiler. 

Q. How often should it be blown out? A. Three or four times 
a day, in the morning before starting, and at noon. 

Q. Of what use is a steam dome on a boiler? A. For storage 
of dry steam. 



HANDBOOK ON ENGINEERING. 64^ 

Q. What is the object of a safety-valve on a boiler? A. To 
relieve over pressure. 

Q. What is your duty with reference to it ? A. To raise it once 
a day and see that it is in good order. 

Q. What is the use of a check valve on a boiler? A. To pre- 
vent the water from returning back into the pump or injector 
which feeds the boiler. 

Q. Do you think a man-hole in the shell on top of a boiler 
weakens it any? A. Yes, to a certain extent. 

Q. What effect has cold water on hot boilerplates? A. It 
will crack or fracture them. 

Q. Where should the gauge cocks be located? A. The lowest 
gauge cock ought to be placed about 3 inches above the top row of 
flues. 

Q. How would you have your blow-off located ? A. In bottom 
of mud drum or boiler. 

Q. How would you have your check valve arranged? A. With 
a stop cock between check and boiler. 

Q. How many valves are there in a common plunger force pump ? 
A. Two — a receiving and a discharge valve. 

Q. How are they located? A. One on the suction side, the 
other on the discharge. 

Q. How do you find the proper size of safety valves for boil- 
ers? A. Three square feet of grate surface is allowed for one 
inch area of spring-loaded valves, or two square feet of grate 
surface to one inch area of common lever valves. 

Q. Give the reasons why pumps do not work sometimes? A. 
Leak in suction, leak around plunger, leaky check valve, or valves 
out of order, or lift too long. 

Q. How often ought boilers to be thoroughly examined and 
tested? A. Twice a year. 

Q. How would you test them? A. With hammer and with 
hydrostatic test — using warm water. 



648 HANDBOOK ON ENGINEERING, 

Q. Describe the single acting {jlunger pump ; how it gets and 
discharges its water? A. The plunger displaces the air in the 
suction pipe, causing a vacuum, which is filled by the atmosphere 
forcing the water therein ; the receiving valve closes and the 
plunger forces the water out through the discharge valve. 

Q. What is the most economical boiler feeder? A. An 
Exhaust Injector. 

Q. What economy is there in the Exhaust Injector? A. 
From 15 to 25 per cent saving in fuel. 

Q. Where is the best place to enter the boiler with the feed 
water? A. Below the water level, but so that the cold water can- 
not strike hot plates. If injector is used this is not so material, 
as the feed water is always hot. 

Q. What are the principal causes of priming in boilers? A. 
Too high water, not steam room enough, misconstruction, engine 
too large for boiler. 

Q. How do you change the water in the boiler when steam is 
up? A. By putting on more feed and opening the surface 
skimmer or blow-off valve. 

Q. If the safety valve was stuck how would you relieve the 
pressure on the boiler if the steam was up and could not make its 
escape? A. Work the steam off with engine after covering fires 
heavy with coal or ashes, and when the boiler is sufficiently cool, 
put safety valve in working order. 

Q. If water in boiler is suffered to get low, what may be the 
result? A. Burn top of tubes, perhaps cause an explosion. 

Q. If w^ater is allowed to get too high, what result? A. 
Cause priming, perhaps cause breaking of cylinder head. 

Q. What are the principal causes of foaming in boilers? A. 
Dirty and impure water and animal oil or grease. ] 

Q. How can foaming in boilers be stopped? A. Close throttle 
and keep closed long enough to show true level of water. If that 
level is sufficiently high, feeding and blowing off will usually 
suffice to correct the evil. 



HANDBOOK ON ENGINEERING. 649 

Q, What would you do if you should find your water gone 
from sight very suddenly? A. If a light fire draw and cool off 
as quickly as possible ; if a heavy fire cover with wet ashes or 
slack coal. Never open or close any outlets of steam when your 
water is out of sight. 

Q. What precautions should you take to blow down a part of 
the water in your boiler while running with a good fire? A. 
Never leave the blow-off valve, and watch the water level. 

Q, How much water would you blow off at once while running ? 
A. Never blow off more than one gauge of water at a time while 
running. 

Q. What precautions should the engineer take when necessary 
to stop with heavy fires.? A. Close dampers, put on injector 
or pump, and if a bleeder is attached, use it. 

jQ. What is an engineer's first duty on entering a boiler-room? 
A. To ascertain the true water level, and look at steam gauge. 

Q. When should a boiler be blown out? A. After it is cooled 
off — never while it is hot. 

Q. When laying up a boiler what should be done? A. Clean 
thoroughly inside and out ; remove all ' ' Rust ' ' and paint rust 
places with red lead ; examine all stays and braces to see if any 
are loose or badly worn. 

Q. Of what use is the indicator? A. The indicator is used to 
determine the power developed by an engine, to serve as a guide 
in setting valves and showing the action of steam in the cylinder. 

Q. How would you increase the power of an engine? A. To 
increase the power of an engine, increase the speed, or get higher 
pressure of steam ; or use less expansion. 

Q. How do you find the horse-power of an engine? 
_ area of piston X M.E.P. X piston speed. 
33,000. 

Q. Which has the most friction, a perfectly fitted, or an im- 
perfectly fitted valve or bearing? A. An imperfect one. 



650 HANDBOOK ON ENGINEERING, 

Q. How hot can you get water under atmospheric pressure with 
exhaust steam ? A. 212°. 

Q. Does pressure have any influence on the boiling point? A. 
Yes. 

Q. Which do you think is the best economy, to run with your 
throttle wide open or partly shut? A. Always have the throttle 
wide open on a governor engine. 

Q. At what temperature has iron the greatest tensile strength? 
A. About 600°. 

Q. About how many pounds of water are required to yield one 
horse-power with our best engines? A. From 15 to 30. 

Q. What is meant by atmospheric pressure? A. The weight 
of the atmosphere. 

Q. What is the weight of atmosphere at sea level? A. 14.7 
pounds. 

Q. What is the coal consumption per hour per indicated horse- 
power? A. Varies from IJ to 7 lbs. 

Q. What is the consumption of coal per hour on a square foot 
of grate surface? A. From 10 to 12 lbs. 

Q. What is the water consumption in pounds per hour per 
indicated horse-power? A. From 15 to 45 lbs. 

Q. How many pounds of water can be evaporated with one 
pound of best soft coal? A. From 7 to 10 lbs. 

Q. How much steam will one cubic inch of water evaporate 
under atmospheric pressure? A. One cubic foot of steam 
( approximately) . 

Q. What is the weight of a cubic foot of fresh water? A. 
62.425 lbs. 

Q. What is the weight of a cubic foot of wrought iron? A. 
480 lbs. 

Q. What is the last thing to do at night before leaving the 
plant? A. Look around for greasy waste, hot coals, matches, oi 
anything which could fire the building. 



HANDBOOK ON ENGINEERING. 651 

Q. What is the weight of a square foot of one-half inch boiler 
plate? A. 20 lbs. 

Q. How much wood equals one ton of soft coal for steam pur- 
poses? A. About 4,000 lbs. of wood. 

Q. What is the source of all power in the steam engine? A, 
The heat stored up in the coal. 

Q. How is the heat liberated from the coal? A. By burning 
it — that is, by combustion. 

Q. Of what does coal consist? A. Carbon, hydrogen, nitro- 
gen, sulphur, oxygen and ash. 

Q. What are the relative proportions of these that enter into 
coal? A. There are different proportions in different specimens 
of coal, but the following shows the average per cent : Carbon, 
80 ; hydrogen, 5 ; nitrogen, 1 ; sulphur, 2 ; oxygen, 7 ; ash, 5. 

Q. What must be mixed with coal before it will burn? A. 
Air. 

Q. Of what is air composed? A. It is composed of nitrogen 
and oxygen in the proportion of 77 per cent nitrogen to 23 of 
oxygen. 

Q. What parts of the air mix with what parts of coal? A. 
The oxygen of the air mixes with the carbon and hydrogen of the 
coal. 

Q. How much air must mix with coal? A. 300 cubic feet of 
air for every pound of coal. 

Q. How many pounds of air are required to burn one pound of 
carbon? A. From 20 to 24, generally taken at 24. 

Q. How many pounds of air to burn one pound of hydrogen? 
A. Thirty-six. 

Q. Is hydrogen hotter than carbon? A. Yes, 4i times hotter. 

Q. What part of the coal gives out the most heat? A. The 
hydrogen does part for part, but as there is so much more of 
carbon than hydrogen in the coal, we get the greatest amount of 
heat from the carbon. 



652 HANDBOOK ON ENGINEERING. 

Q. In how many different ways is heat transmitted? A. 
Three, by radiation, by conduction and convection. 

Q. If the fire consisted of glowing fuel, show how the heat 
enters the water and forms steam ? A. The heat from the glow- 
ing fuel passes by radiation through the ah' space above the fuel 
to the furnace crown ; there it passes through the iron of the 
crown by conduction ; there, it warms the water resting on the 
crown, which then rises and parts with its heat to the colder water 
by conduction till the whole mass of water is heated ; then the 
heated water rises to the surface and parts with its steam, so a 
constant circulation is maintained by convection, 

Q. Of what does water consist? A. Oxygen and hydrogen. 

Q. In what proportion? A. Eight of oxygen to one of 
hydrogen, by weight. 

Q. What are the different kinds of heat? A. Latent heat, 
sensible heat and sometimes, total heat. 

Q. What is meant by latent heat? A. Heat that does not 
affect the thermometer and which expends itself in changing the 
nature of a body, such as turning ice into water or water into steam. 

Q. Under what circumstances do bodies get latent heat? A. 
When they are passing from a solid state to a liquid state, or from 
a liquid to a gaseous state. 

Q. How can latent heat be recovered? A. By bringing the 
body back from a state of gas to a liquid, or from that of a liquid 
to that of a solid. 

Q. What is meant by a thermal unit? A. The heat necessary 
to raise one pound of water, at any temperature — one degree 
Fah. 

Q. If the power is in coal, why should we use steam? A. Be- 
cause, steam has some properties which make it an invaluable 
agent for applying the energy of the heat to the engine. 

Q. What is steam? A. It is an invisible elastic gas generated 
from water by the application of heat. 

Q. What are the properties which make it so valuable to us? 



HANDBOOK ON ENGINEERING. 653 

A.. 1. The ease with which we can condense it. 2. Its great 
expansive power. 3. The small space it occupies when con- 
densed. 

Q. Why do you condense the steam? A. To form a vacuum 
and so destroy the back pressure that would otherwise be on the 
piston, and thus get more useful work out of the steam. 

Q. What is vacuum? A. A space void of all matter. 

Q. How do you maintain a vacuum? A. By the steam used 
being constantly condensed by the cold water or cold tubes, and 
the air pump constantly clearing the condenser out. 

Q. Why does condensing the used steam form a vacuum? A. 
Because a cubic foot of steam at atmospheric pressure shrinks 
into about a cubic inch of water. 

Q. What do you understand by the term horse-power ? A, A 
horse-power is equivalent to raising 33,000 lbs. one foot per min- 
ute, or 550 lbs. raised one foot per second. 

Q. What do you understand by lead on an engine's valve? A. 
Lead on a valve is the admission of steam into the cylinder be- 
fore the piston starts its stroke. 

Q. What is the clearance of a cylinder as the term is applied 
at the present timer A. Clearance is the space between the 
cylinder head and the piston head, with ports included. 

Q. What are considered the greatest improvements on the 
stationary engine in the last forty years? Ao The governor, the 
Corliss valve gear, and the triple compound expansion. 

Q. What is meant by triple expansion engine ? A. A triple 
expansion engine has three cylinders, using the steam expansively 
in each one. 

Q. Is there any danger of a well-fitted and tightly-keyed fly- 
wheel coming loose? A. Yes ; water in the cylinder by produc- 
ing a heavy jar would tend to loosen a fly-wheel and frequently 
reversing an engine under a load and high speed, would tend to 
produce the same effect. 



654 HANDBOOK ON ENGINEERING. 

Q. What is a condenser as applied to an engine? A. The con- 
denser is a part of the low-pressure engine, and is a receptacle 
into which the exhaust enters and is there condensed. 

Q. What are the principles which distinguish a high-pressure 
from a low-pressure engine? A. Where no condenser is used and 
the exhaust steam is open to the atmosphere. 

Q. About how much gain is there by using the condenser? A. 
17 to 25 per cent, where cost of water is not figured. 

Q. What do you understand by the use of steam expansively? 
A. Where steam admitted at a certain pressure is cut off and 
allowed to expand to a lower pressure. 

Q. How many inches of vacuum give the best results in a con- 
densing engine? A. Usually considered 25". 

Q. What is meant by a horizontal tandem engine? A. One 
cylinder being behind the other, with two pistons on same rod. 

Q. What is a Corliss valve gear ? A. (Describe the half moon, 
or crab-claw gear, or oval-arm gear with dash pots.) 

Q. From what cause do belts have the power to drive shafting? 
A. By friction or cohesion. 

Q. What do you understand by lap? A. Outside lap is that 
portion of valve which extends beyond the ports when valve is 
placed on the center of travel ; and inside lap is that portion of 
valves which projects over the ports on the inside or towards the 
middle of valve. 

Q. What is the use of inside lap? A. To give the engine 
compression. 

Q. Where is the dead center of an engine? A. The point 
where the crank and the piston rod are in the same right line. 

Q. In what position would you place an engine to take up any 
lost motion of the reciprocating parts ? A. Place the engine in 
the position where the least wear takes place on the journals. 
That is, in taking up the wear of crank-pin brasses, place the 
§n^ine oi> either dead center, as when runnings there is little wear 



HANDBOOK ON ENGINEERING. Q55 

upon the crank-pin at these points. If taking up the cross-head 
pin brasses — without disconnecting and swinging the rod — 
place the engine at half stroke, which is the extreme point of 
swing of the rod, there being the least wear on the brasses and 
cross-head pin in this position. 

Q. What benefits are derived from using fly-wheels on steam 
engines ? A. The energy developed in the cylinder while the steam 
is doing its work, is stored up in the fly-wheel, and given out by 
it while there is no work being done in the cylinder — that is, 
when the engine is passing the dead centers. This tends to keep 
the speed of the engine shaft steady. 

Q. Name several kinds of reducing motions, as used in indi- 
cator practice? A. The pantograph, the pendulum, the brumbo 
pulley, the reducing wheel. 

Q. How can an engineer tell from an indicator diagram whether 
the piston or valves are leaking? A. Leaky steam valves will 
cause the expansion curve to become convex ; that is, it will not 
follow hyperbolic expansion, and will also show increased back 
pressure. But if the exhaust valves leak also, one may offset the 
other, and the indicator diagram would show no leak. A leaky 
piston can be detected by a rapid falling in the pressure on the 
expansion curve immediately after the point of cut-off. It will 
also show increased back pressure. A falling in pressure in the 
upper portion of the compression curve shows a leak in the exhaust 
valve. 

Q. What would be the best method of treating a badly scaled 
boiler, that was to be cleaned by a liberal use of compound? A. 
First, open the boiler up and note where the loose scale, if any, 
has lodged. Wash out thoroughly and put in the required 
amount of compound. While the boiler is in service, open the 
blow-off valve for a few seconds, two or three times a day, to be 
assured that it does not become stopped up with scale. After 
running the boiler for a week^ shut it down, and ^vhen the^ 



656 HANDBOOK ON ENGINEERING. 

pressure is down and the boiler cooled off, run the water out and 
take off the hand-hole plates. Note what effect the compound 
has had on the scale, and where the disengaged scale has lodged. 
Wash out thoroughly and use judgment as to whether it is advis- 
able to use a less or greater quantity of compound, or to add 
a small quantity daily. Continue the washing out at short 
intervals, as many boilers have been burned by large quan- 
tities of scale dropping on the fire sheets and not being 
removed. 

Q. What is an engineer's first duty upon taking charge of a 
steam plant? A. The first duty of an engineer assuming charge 
of a steam plant is to familiarize himself with his surroundings, 
ascertain the duty required of each and every piece of machinery 
contained therein, and in just what condition each one is. 
Let us discuss it at length, assuming that when just engaged he 
is informed as to the nature of the work required of the plant 
in question, namely: Whether it is a heating plant, electric 
lighting, hydraulic or electric elevator, power station, or any 
other kind of the various steam plants in existence. Of course, 
a great deal depends upon the size and kind of plant under con- 
sideration and the number of men employed, hours in operation, 
and some other things in general which most engineers know of. 
He should first see just what his plant contains " from cellar 
to garret," so to speak ; whether all that is contained has to run 
continually, or almost so, and what can be depended on in case 
anything should suddenly become deranged or give out entirely. 
Next, he should ascertain the general condition of everything, 
going over each portion in turn, as time and opportunity i3ermit, 
and conclude from what he has seen how much longer it ma}^ 
be run safely and economically. It will be remembered that a 
piece of machinery may be run safely and yet not with economy. 
So, if he should wait for the safety limit to be reached, 
without taking other things into consideration, he might wait 



HANDBOOK ON ENGINEERING. 657 

a long time aud iu so doing waste many dollars of his 
employer's money before it was thought necessary to reno- 
vate, repair or renew. In going over everything, examining 
each part critically, it would be well to make copious notes, and, 
I might add, sketches, to which the engineer can again refer. 
It sometimes happens that engineers, in making an examination 
of machinery, do not take dimensions or make sketches of certain 
parts which have to be repaired, or perhaps renewed, thinking 
that the next time the apparatus is looked at will do for that. 
Now, it sometimes happens that the " next time " is the time 
when some accident occurs, finding you unprepared, causing con- 
fusion, in the midst of which the making of sketches and taking 
of dimensions cannot be thought of. All such should be done at 
the first opportunity, and spare parts of the different machinery 
should be kept on hand, especially in the case of a plant which 
has only the machinery which is constantly in use. Another point 
of importance to which an engineer should give attention, is to 
ascertain the quantity and kind of supplies which are on hand, 
that he may know when to make requisition for more, and so not 
run short, as he otherwise might do. It is also important to see 
w^hat tools the plant contains and upon what you can depend in 
case of the break-down of any part of the machinery. Of course 
all the above cannot be done in one day, but no time should be 
lost in doing all these things as early as possible, for the sooner 
you get all the particulars and details of your plant at your 
"fingers' ends," the lighter will be your own labors, and the 
more free will your mind be to think and act intelligently for the 
emergencies of the future. Therefore, by performing this first 
duty as early and thoroughly as possible, the succeeding ones will 
be comparatively easy to handle and perform, for the reason that 
you will be prepared for them. 

Q. Define and explain the difference between sensible and 
latent heat? A. The difference between sensible and latent heat 



658 HANDBOOK ON ENGINEERING. 

is explained thus : Sensible heat may be measured with a ther- 
mometer, that is, it affects the mercury in a thermometer, caus- 
ing it to rise in the stem so that the degree of heat may be 
measured on the graduated scale affixed. Latent heat does not 
affect the thermometer. Bodies get latent heat when they are 
passing from a solid state to a liquid state, and also when passing 
from a liquid to a gaseous state ; and moreover, this latent heat 
can be recovered by bringing a body back from a gaseous to a 
liquid state, and from liquid to solid. Water is most com- 
monly seen under the three forms of matter just mentioned, 
namely, solid, ice ; liquid, water ; gaseous, steam. The following 
method has been used to explain how latent heat exists : 
A quantity of powdered ice is placed in a vessel and brought 
into a very warm room. As long as it remains as ice, it may be 
any degree of heat below 32° Fahr., but the instant it begins to 
melt, owing to the heat of the room, a thermometer placed in it 
will record 32° Fahr. The thermometer will continue at 32° as long- 
as there is any ice in the vessel, but just as soon as the last piece of 
ice has melted it will begin to rise, and continue to do so until the 
water boils, when it will stand at 212° ; but although the water 
goes on receiving heat after this, the instrument will stand at 212° 
until all the water has boiled away. Now, a great amount of heat 
must have entered the water since the ice began to melt, but it has 
no effect on the thermometer, which continues at 32°, as noted 
above ; the heat that has so entered is called ' ' the latent heat of 
water." The heat that has entered the water from boiling 
till it all becomes steam is called the " latent heat of steam." 
The latent heat of water has been found to be 143° Fahr. 
and the latent heat of steam, at the pressure of the atmosphere, 
is 966°. This is the way the above was determined: A 
quantity of water at a temperature of 32° Fahr. is made to 
boil, and the time taken to do so noted ; in this case, it took one 
hour. The water must be kept boiling until it has all evaporated, 



HANDBOOK ON ENGINEERING. 659 

and the time noted from boiling till evaporation, which in this 
case will be 5 a hours. Therefore, 

Temperature of boiling point, . . . . 212° 

Temperature of water at first, 32° 

Heat that has entered the water in one hour, . . o . 180° 
Number of hours boiling, o . . 5\ 

900 
60 

Heat that has entered during the 5i hours, . , . . 960° 

From this we see that the heat necessary to form steam, instead 
of being only 212°, must be 966° + 212° = 1178°, or 51 times as 
great. Therefore, if it were not for latent heat, we would require 
to burn 51 times the amount of coal that we now do to generate 
steam. The sensible and latent heats alter with the pressure, but 
as the sensible increases the latent decreases, and, roughly 
speaking, the total heat, or the sum of the two, is the same. In 
connection with the foregoing questions, I would recommend the 
reader to spend a little time in looking over the " steam tables," 
and make comparisons between the different quantities noted 
therein. By so doing he will get an exact knowledge of the prop- 
erties of saturated steam. 

Q. Explain the term " clearance," as used in connection with 
an engine cylinder ? A. There are two kinds of clearance, cylinder 
clearance and piston clearance . Cylinder clearance means the space 
or volume which exists between the piston and the valve, when 
the piston is exactly at the beginning of the stroke and the crank 
is on the dead center. This volume can be found by taking care- 
ful and exact measurements and making calculations from them, 
but a more correct way is to fill the space with water, noting the 
quantity used, and so make calculations to find the cubic con- 



660 HANDBOOK ON ENGINEERING. 

tents. The cubic contents of the clearance space is a certain per- 
centage of the total volume of the cylinder itself and such clear- 
ance is expressed as so much per cent. This clearance causes a 
small loss of steam each stroke, owing to the difference between 
the initial and compressive pressure. Piston clearance is the 
space between the piston and cylinder head when the crank is on 
the dead center. This clearance is necessary to prevent the 
cylinder head being knocked out, in case of an unusual quantitv 
of water gaining entrance to the cylinder while the engine is 
running at its usual speed ; and also to admit of the crank-pin 
and wrist-pin brasses being keyed up at certain intervals. The 
way to find the piston clearance of an engine is as follows : 
First, disconnect the wrist-pin end of the connecting rod from 
the cross-head, and with a bar push back the cross-head until 
the piston strikes the cylinder head ; then make a mark with 
a scriber or sharp chisel, on both the sides of the cross-head and 
on the guide in which the cross-head runs ; these marks must be 
exactly in line with each other while the piston is in the above 
stated position. Next, move the piston to the other end of the 
cylinder till it strikes the head, and make a mark on the guide 
similar to that on the other end, using the same mark which was 
made on the cross-head. The new mark must also be in line with 
this, as at the first mentioned end. You now have a mark at 
each end of the guide, which represents the place at which the 
piston strikes the cylinder head, when they alternately coincide 
with the mark on the cross-head itself. Now, connect the rod 
to the cross-head again and place the engine or crank on the center. 
Next, produce or extend the mark on the cross-head to the guide, 
this time using a pencil instead of a chisel and scriber. The 
distance between the new pencil mark and the first mark made 
on the guide is the amount of piston clearance which exists at 
that end of the cylinder. Repeat the operation on the other end 
and ycu will obtain the clearance existing there. If these clear- 



HANDBOOK ON ENGINEERING. 661 

ances are not equal, as indicated by the marks, make them so 
by the means provided for in the design of the piston rod and 
crosshead. After the clearance has been equalized, the pencil 
marks may be obliterated and marks similar to the first ones may 
be cut in, thus leaving a permanent mark which can be seen while 
the engine is running, and from which can be determined whether 
the clearance is lessening, and at which end. 

Q. What is the pressure of the atmosphere at the sea level, and 
how determined? A. The pressure of the atmosphere is generally 
spoken of as 15 lbs. per square inch, but as the pressure of the 
atmosphere is constantly varying at any one spot, corrections 
have to. be made according to the reading of a barometer. 
Generally speaking, 15 is as nearly correct as engineers require 
it. The pressure of the atmosphere can be ascertained by the 
following experiment: Take a glass tube about 33 inches long, 
having a bore equal to a square inch in section. Let one end of 
the tube be closed in or capped, so that it can contain a fluid. 
Then fill it with pure mercury, carefully expelling any air bub- 
bles. When it is full, cover the open end of the tube with a piece 
of glass and invert the whole tube. Place the open end into a 
cup of mercury, the surface of which is subject to the pressure of 
the air, and then withdraw the piece of glass. The mercury in 
the tube will drop about three inches and then stop. When it 
has ceased to fall, again cover the end of the tube with the glass. 
Lift the tube out of the cup and remove the glass so that the 
mercury may run out into a scale-pan provided for that purpose. 
Upon actually weighing the mercury lately contained in the tube, 
it will be found to weigh 14.7 lbs. The mercury will stop falling 
in the tube at 30 inches, or at the sea level. Hence, we know 
that the atmosphere balances, or exerts a pressure of 14.7 lbs. 
per square inch at the sea level. 

Q. Upon what does the efficiency of a surface condenser de- 
pend ? A. The efficiency of a surface condenser depends upon : 



662 HANDBOOK ON ENGINEERING. 

1st, the proj^er amount of cooling surface ; 2d, the rapidity with 
which the water is made to circulate through the tubes ; 3d, the 
water being made to flow in an opposite direction to the steam. 
The temperature of the circulating water also has a bearing on 
the question, as it is obvious that the colder the water the more 
effective it will be in condensing the steam. 

Q. A feed pump has a steam cylinder of 6 inches in diameter, 
and water cylinder of 4 inches diameter ; assuming the steam 
pressure carried to be 80 lbs. per square inch throughout the 
stroke, what will be the balancing pressure per square inch 
against the water piston, friction being entirely neglected, and 
gauge pressure being used? A. In this question, we first find 
the area, the number of square inches contained in the steam 
piston. Thus ; The diameter rr= 6 in. and 6^ x .7854 = the area. 
Worked out it appears thus: 6^ means that 6 is to be 
squared, or multiplied by itself, or 6x6 = 36 square inches, 
and 36 square inches multiplied by the constant .7854 = 
28.27 square Inches area contained in the steam piston. 
Since the pressure is stated to be 80 lbs. per square inch, then 
28.27 X 80 =: total pressure on the piston in pounds, or 2261.60 
lbs. Now, we will find the area of the water piston, which is 4 
inches in diameter, 4^ x .7854 = 12.5664 square inches contained 
in the water piston. Therefore, the water piston, with an area 
of 12.56 sq. in., has to have a resistance against which it will act 
of 2261.60 lbs., in order to balance the pressure against the 
steam piston. Hence, the pressure per square inch can be found 
by dividing 2261.60, or 2261.60 divided by 12.56 = 180 lbs. per 
square inch, the balancing pressure on the 4-inch water piston. 

Q. State what you consider a good standard of strength for 
steel boiler plate? A. The American Boiler Makers' standard, 
as used, is as follows: Tensile strength, from 55,000 to 60,000 
lbs. per square inch section ; elongation in 8 inches, 20 per cent 
for plates | inch thick, and under ; 22 per cent for plates f to f 



HANDBOOK ON ENGINEEKING. 663 

inches ; 25 per cent for plates | inch and under ; the specimen 
test piece must bend back on itself when cold, without showing 
signs of fracture ; for plates over i inch thick, specimens must 
withstand bending 180° (or half way) round a mandrel IJ times 
the thickness of the plate. The chemical requirements are as 
follows: Phosphorus, not over .04 per cent; sulphur, not over 
.03 per cent. 

Q. What is meant by the heating surface of a boiler? A. The 
heating surface of a boiler is that surface of plates or tubes on 
one side of which is water, and on the other hot gases. It has 
been decided that the surface next the water shall be reckoned, 
the value to be given in square feet. In a fire tube, or tubular 
boiler, it will include the under side of the shell from fire-line to 
fire-line (usually about one-half of it), the tubes and such part of 
the back-tube sheet as is below the back arch and not taken up 
by the tube ends. For a water-tube boiler, the heating sur- 
face will include the tubes, such part of the headers as are 
in contact with the hot gases, and the lower part (about one- 
half) of the steam drum. In calculating the heating surface, 
none should be taken which has steam on one side and hot gases 
on the other, as such parts tend to superheat the steam, and are 
known as superheating surfaces. 

Q. What is a boiler horse-power? A. A boiler horse-power 
has been recently defined as the evaporation of 34| pounds of 
water per hour from a feed water temperature of 212° Fahr. 
into steam at a temperature of 212° Fahr., and at a pressure of 
one atmosphere. Under these conditions each pound of water 
evaporated will take up 966 heat units, and the 341 lbs. will take 
341 X 966 = 33,327 heat units per hour. Hence, to find the 
horse-power of a boiler, it is necessary to find the heat units 
delivered per hour to the water and divide that number by 33,327. 

Q. What will be the heating surface of a fire-tube boiler 6 
feet in diameter, having 150 tubes 3 inches in diameter and 15 



664 HANDBOOK ON ENGINEERING. 

feet long? A. Each tube will have a heating surface equal to its 
outside area, since the water is on the outside of the tubes. The 
area of a cylinder 3 in. in diameter and 15 ft. long will be the 
circumference times the length ; 3 in. = J ft. and the circumfer- 
ence = 3.1416 xi = .7854 ft.; this, times the length 15 ft. 
= 11.78 sq. ft. for one tube ; for 150 tubes, it will be 150 times 
that = 1767 sq. ft. The lower half of the shell is usually con- 
sidered as heating surface. The circumference of a circle 6 ft. in 
diameter is 6 x 3.1416 = 18.85 ft. and the area of the shell = 
18.85x15=282.75 sq. ft. Half this will be 141.37 sq. ft. 
For the back end or tube plate, the total area will be the diameter 
squared times .7854 = 6^ x .7854 = 28.27 sq. ft. ; | of this will 
be below the arch, and f of 28.27 = 18.85 sq. ft. From this 
must be subtracted the area of the ends of the tubes. The end 
area of one tube is (i)^ x .7854 = .049 sq. ft., and for 150 
tubes it is 150 times that, or 7.35 sq. ft. The heating surface of 
the tube plate will then be 18.85 minus 7.35 = 11.5 sq. ft. The 
front tube plate is not considered, because the gases are cooled 
too much to be effective by the time they have passed through 
the tubes. The total heating surface is 1767 + 141.37 + 11.5 
= 1919.87 sq. ft. 

Q. On what does the efficiency of a boiler depend? A. The 
efficiency of any piece of machinery is the ratio of the energy made 
useful to that furnished. The object of the boiler is to make steam ; 
hence, the enegy used is that which has gone into the steam. The 
proportion of the heat generated in the furnace which is transferred 
to the steam, will depend on the thickness of the plates of the 
boiler, on their condition as to cleanliness, on the amount of time 
during which the gases are in contact with the plates in their 
passage from furnace to chimney, on the completeness with which 
all parts of the gases are brought in contact with the plates, and on 
the temperature of the hot gases. Evidently, heat will pass through 
a thin plate more readily than through a thick one, and more 



HANDBOOK ON ENGINEERING. 665 

rejidily through a clean plate than through one on which a non- 
conducting coating of soot or scale has formed ; the more time 
available for the transfer of heat, the greater will be the amount 
transferred ; the more complete the contact between plates and 
gases, the more opportunity will there be for the transfer of heat, 
and the higher the temperature of the gases, the more rapidly 
will the heat be transferred. To have a boiler efficient, it is 
necessary to have plenty of heating surface, so that the hot gases 
will have time for contact, to keep the plates clean, to have good 
circulation of the gases, and to keep their temperature high by 
Ijreventing radiation and allowing as little air to enter the furnace 
as is needed for good combustion. The efficiency of the furnace, 
that is, the ratio of the heat generated in the furnace to that con- 
tained in the coal, is a separate matter, though often the two are 
lumped together. It depends on the adaptation of the furnace to 
the kind and size of coal used, on the size of the combustion 
chamber and on the proper firing of the coal. 

Q. On what its satisfactory working? A. In order to 
work satisfactorily, a boiler must not only be efficient, but must 
make steam rapidly, must make dry steam, must be easily fired 
and cleaned, and must be capable of standing a considerable 
amount of forcing without serious priming. To get rapid steam 
making, it is necessary to have good circulation of the water in the 
boiler ; to get dry steam, plenty of steam space is needed, so that 
the steam may circulate slowly and allow the water to drop out of 
it ; easy firing means a low fire door of good size, and a rather 
short grate; easy cleaning means accessible parts, good sized 
man-holes, good sized and well placed hand-holes, a large blow- 
off and a short boiler ; the prevention of priming when carrying 
an overload is a difficult matter ; the tendency to such an occur- 
rence depends largely on the feed-water used ; plenty of steam 
space and good circulation are helpful, but some waters will foam 
in spite of all precautions. 



me 



HANDBOOK ON ENGINEERING. 



cut- 
off is desired, how would you proceed? A. Put on a new valve 
with more outside laj^. This would require a greater travel of the 
valve, consequently, I would increase the throw of the eccentric, 
also. 

Q. Which requires the greater outside lap, cutting off at -^^ of 
the stroke, or cutting off at J? A. Cutting off at y9_. The 
earher the cut-off, the greater should be the outside lap. 

Q. Are all plain slide valves made alike, as regards the exhaust 
cavity of the valve? A. No ; sometimes they are made " line and 
line " inside, that is, the width of the exhaust cavity is equal to 
the distance between the inner edges of the two steam ports ; and 
again, the width of the exhaust cavity is made greater or less than 
this distance, according as an earlier or later release is desired. 

Q. What is the effect of giving inside lap to a slide valve? A. 
It delays the release and increases the compression. 

Q. What is the effect of giving inside lead to a slide valve? 
A. It gives an early release and decreases the compression. 

Q. Suppose a simple slide valve engine with a fly-ball governor, 
and the governor belt should break or slip off, what would 
happen? A. If it were a plain governor the engine would race; 
but if a governor with an automatic stop, the engine would slow 
down and stop. 

Q. What two forces are opposed to each other in a case of fly- 
ball governor? A. Centrifugal force, tending to throw the balls 
away from the governor staff, and the force of gravity, tending to 
draw the balls to the staff. 

Q. What other name is given to a fly-ball governor? A. It is 
also called a throttling governor, because the steam in passing 
through the governor valve is throttled, choked, or wire- 
drawn. 

Q. Are all fly-ball governors throttling governors? A. No; 
the governor of a Porter-Allen engine and those of all Corliss 



HANDBOOK ON ENGINEERING. 667 

engines, while of tlie fly-ball type, are not throttling governors, 
because the steam does not pass through them. 

Q. If the governor shaft of a fly-ball governor on a plain slide- 
valve engine should break, could the engine be run? A. Yes; 
by regulating the speed of the engine by hand at the throttle- 
valve. 

Q. Describe an automatic cut-off engine? A. In this class of 
engines, as the load on the engine becomes greater or less, the 
steam entering the cylinder is cut off later or earlier, and it is 
done through a fly-ball governor in the case of a Corliss engine, 
or through a shaft-governor or regulator in the case of a high- 
speed engine. 

Q. In an automatic cut-off high-speed engine with shaft-gov- 
ernor, is the eccentric fastened to the shaft? A. It is not. It 
is so arranged as to move freely across the shaft, in order to per- 
mit the center of the eccentric to approach or to recede from the 
center of the shaft, according as the load on the engine decreases 
or is increased. And herein lies the chief difference between a 
plain slide-valve and an automatic cut-off slide-valve engine. 

Q. If the connecting rod of an engine had box liners at both 
ends and in taking it down the liners were all mixed up, how 
could the length of the rod from center to center of boxes be 
found? A. Put the cross-head in the middle of its stroke — 
after finding the piston striking points — and then measure from 
the center of the cross-head wrist to the center of the main shaft. 
If the piston clearance at both ends of the cylinder is known, the 
piston may be pushed to the crank end of the cylinder until it 
touches the head, and the distance from the center of the cross- 
head wrist to the center of the main shaft found, to which should 
be added the length or throw of the crank, and also the piston 
clearance at the crank end of the cylinder. 

Q. But suppose it were more convenient to push the piston to 
the head end of the cylinder, what then? A. Find the distance 



668 HANDBOOK ON ENGINEERING. 

from the center of cross-head wrist to center of main shaft and 
deduct the throw of the crank, and also the clearance. 

Q. How is the length of the valve stem and of the eccentric 
rod found for a plain slide valve engine having a rock shaft? A. 
If the motion of the slide valve is parallel with the motion of the 
piston, the length of the valve stem may be found by measuring 
in a horizontal line from the center of the valve seat to the center 
of the rock shaft ; and for the eccentric rod by measuring from 
the center of the rock shaft, horizontally, to the center of the 
main shaft, which would include one-half the yoke. 

Q. What is a direct, and also an indirect valve motion ? A. 
When there is no rock shaft between the eccentric and the valve 
to compound the motion, it is called " direct," and when a rock 
shaft intervenes, it is called an " indirect " valve motion. 

Q. Is the valve motion of a Corliss engine direct or indirect? 
A. It is direct. 

Q. How so ; it has a rock shaft between the eccentric and 
the wrist plate? A. Even so, it is a direct valve motion ; because 
all connections to the rock-shaft arm are above the center of the 
shaft, consequently, the motion is simple and not compound. 

Q. When is an engine said to " run under," and when to " run 
over? " A. When the crank pin is above the center of the main 
shaft and the pin moves towards the cylinder, the engine is said 
to " run under ; "and when it moves away from the cylinder, the 
engine is said to " run over." 

Q. What is meant by lead of valve, and what is it for? A. 
Lead is the amount that the port is open to steam when the crank 
is on its center. It is given in order to allow the full pressure of 
steam to come on the piston at the beginning of the stroke, and 
to provide a cushion for the piston. 

Q. Could not cushion for the piston be obtained in some other 
manner? A. Yes, by producing compression by an early closing 
of the exhaust. 



HANDBOOK ON ENGINEERING. 



669 



Q. Supj)ose a slide valve had |" lap and no lead, and it was 
desired to give it ^^" lead, how should it be done? A. By mov- 
ing the eccentric. 

Q. Why could it not be done by altering the length of the 
eccentric rod ? A. Because the eccentric rod does not establish 
the amount of lead ; it simply equalizes the lead given by 
moving eccentric. 

Q. How would you test the piston of a steam engine to see 
whether it was steam-tight or not? A. Pat the crank on the 
outboard center ; remove the cylinder head on the head end ; 
block the cross-head and admit steam to the crank-end of 
cylinder and note the effect. The fly-wheel, or the cross-head 
may be securely blocked and the piston tested in this manner at 
different points in the stroke. 

Q. Why are two eccentrics and two wrist plates put on some Corliss 
engines? A. One eccentric is for the induction valves to lengthen 
the range of the cut-off ; the other for the exhaust valves to admit 
of early release, without excessive compression. With a Corliss 
engine having but one eccentric, the limit of cut-off is at less than 
one-half stroke, but with two eccentrics the cut-off may be still 
later in the stroke, and still release the steam at the proper time. 

Q. What is meant by a "' blocked up " governor on a Corliss 
engine? A. When the safety stop is " in " the governor is said 
to be blocked up. 

Q. With a blocked up governor, suppose the main driving belt 
should break, what would be the result? A. The engine would 
race and would, perhaps, be wrecked. 

Q. What is meant by the fire line of a horizontal cylindrical 
boiler? A. It is the height to which the shell is exposed to the 
action of the flames. 

Q. How high should the fire line be run? A. It may be run as 
high as the lower gauge cock water level, although it is frequently 
run no higher than the top row^ of flues. 



670 HANDBOOK ON ENGINEERING. 

Q. What causes a chimney or smoke-stack to draw ? A. The 
difference in the temperature of the air inside the chimney and 
that outside. The air inside expands and exerts less pressure 
than the outside air, which rushes in to equalize the pressure. 

Q. What does the amount of grate surface determine? A. It 
determines the amount of coal that can be burned per hour, and 
consequently, the amount of steam that can be generated. 

Q. What is the object in giving a slide valve outside lap? A. 
To save steam by cutting off the flow of steam into the cylinder 
before the piston reaches the end of its stroke. For example : 
With 24 in. stroke of piston and | cut-off, the flow of steam to 
the piston is cut off when the piston has moved 15 inches and it 
is driven the remaining 9 inches by the expansive force of the 
steam. 

Q. What amount of refrigerating water is required for a con- 
denser? A. For a surface condenser about 50 times, and for a 
jet condenser 30 times the amount of water evaporated in the 
boiler ; more or less than these quantities being required accord- 
ing to the temperature of the exhaust steam. 

Q. Suppose your condenser was out of order and undergoing 
repairs, could you run the engine? A. Yes; by attaching an 
exhaust pipe to the engine and exhausting into the atmosphere. 

Q. With a lever safety valve, should the end of the valve stem 
upon which the lever rests, be square or concave? A. Neither 
one ; it should be pointed, so that the lever will always bear 
directly on a line with the center of the valve stem. 

Q. What is the proper proportion of a safety valve lever? A. 
About 7 to 1 ; that is, if the distance from the center of the 
valve to the fulcrum is 1 inch, the distance from the center of the 
valve to the end of the long arm of the lever should be about 7 
inches. 

Q. How should the grates be set in a boiler furnace? A. 
They should be set level, because this plan will enable the fire- 



HANDBOOK ON ENGINEERING. 671 

man to more easily carry a bed of fuel of uniform depth ; besides, 
it is less laborious to clean the fire than when the grates are lower 
at the bridge wall. 

Q. What is momentum? A. It is the product of the mass or 
bulk of a moving body, taken in pounds or tons, multiplied by the 
velocity of the moving mass, generally taken in feet per second. 

Q. Will an injector work at the same steam pressure when it 
lifts the water as when the water flows to it under pressure? A. 
No ; when the water flows to an injector under pressure it will 
work down to the lowest steam pressures, but when lifting the 
water it requires a steam pressure of ten pounds or over to work 
the injector. 

Q. What is the greatest height to which an injector will lift 
water? A. That depends upon the starting steam pressure. 
There are injectors that will lift water two feet with 10 lbs. 
steam pressure, five feet with 30 lbs., and from 12 to 25 feet with 
60 lbs. and over. 

Q. If the pulley on the main shaft of an engine driving a fly- 
ball governor be reduced in diameter, what effect will it have on 
the speed of the engine? A. The speed of the engine will be 
increased. 

Q. Which is the greater, the bursting or the collapsing pressure 
of a boiler tube? A. A boiler tube will collapse under less pres- 
sure than would be required to burst it. 

Q. Should a horizontal externally fired boiler be set level or 
with a pitch? A. It is customary to set such a boiler one inch 
lower at the end to which the blow-off pipe is attached, in order 
to drain the boiler readily. 

Q. In a slide valve engine with a connecting rod, will the valve 
cut off the same at both ends of the stroke if it has equal lap and 
lead? A. No ; owing to the angularity of the connecting rod. 

Q. Is it proper to close the damper with a banked fire? A. 
The damper should never be closed tightly while there is fire. 



672 



HANDBOOK ON ENGINEERING. 



CHAPTER XXIII. 
INSTRUCTIONS FOR LINING UP EXTENSION TO LINE SHAFT. 

The erection of a liue shaft, or an extension to one, is a 
job that should have the services of a competent millwright or 
machinist, as it is one calling for experience and considerable 
skill. 

I will^ however, give you some pointers on how to proceed. A 
linen line or fine wire should be stretched beneath the shaft and 
parallel to it, and extending beyond the termination of the 
extension . 



s^c 



Wf* 



3E 



Jrj^^^zfc t 



Oa 



0- 



To set the line parallel to the main line shaft, hang the plumb- 
bobs A A over the shaft, as shown in the sketch, and then adjust 
the line until it just touches the lines supporting the bobs, with- 
out disturbing their position. If the plumb-bobs trouble you by 
swaying, set pails of water so that the bobs will be immersed ; 
this will stop the swaying without destroying their truth. The 
plumb-bobs may just as well be old nuts or similar pieces of iron, 



HANDBOOK ON ENGINEERING. 673 

as the regulation type, since the result will be exactly the same. 
After getting the line adjusted to the desired position, susj^end 
the plumb-bobs A A along the direction of the extension, so that 
their supporting cords will just touch the line without disturbing it. 
The new section of the shaft is now brought in position sideways 
until it also touches the cords of the plumb-bobs -1 A , which, of 
course, locates it parallel with the main shaft in a horizontal plane. 
To get it to the right height, enter the shaft coupling of the new 
part into coupling of the main shaft, and then adjust until the 
shaft shows level when tested with an accurate spirit level. A 
level suitable for this work should be of iron and planed on the 
under side with a V-groove, which will always locate it parallel 
with the shaft when testing it. Before leveling the new part of 
the shaft, it will be necessary to try the shaft already in position, 
as it may not be level. If found " out " it should be leveled, 
but sometimes this will not be possible or feasible, in which case 
it will be necessary to set the new part at the same inclination. 
To do this, test the main shaft and find how much it is out, and" 
adjust the level by strips of paper until it shows " fair." The 
paper should be secured to the level by glue or other means and 
used on the new shaft in that condition, always keeping the level 
with the " packed " end pointing in the same direction. After 
getting the new part in position, it is well to test it before con- 
necting it to the main part ; that is, it should be turned by hand 
to determine if the frictional resistance is excessive or not. After 
connecting with the main j^art, it is not a bad idea to test it again 
by hand, if possible. With a long shaft it may be necessary to 
disconnect the further sections and remove the belts from the 
connected machines. In this way a fair idea of the frictional 
resistance may be obtained. As before stated, this work requires 
experience and skill, and should properly be done by one thor- 
oughly competent for the work ; for, while his services may seem 
a trifle expensiye, it will usyally be found to pay better in the 



674 HANDBOOK ON ENGINEERING. 

long run, as the frictional resistance of an improperly lined shaft 
will quickly consume coal enough to pay the difference. 

SIMPLICITY IN STEAM PIPING. 

In building steam power plants, and especially in arranging 
the piping connections for them, simplicity is a characteristic the 
value of which is often too little appreciated. It should be borne 
in mind that extra valves and duplicate piping mean a very 
considerable amount of capital lying at waste to meet a contin- 
gency which may, in all probability, never arise, not to speak of 
the care and attention required to keep, piping and valves which 
are rarely used in shape for service. Another point which ought 
to be realized in the design of piping, is that every square foot of 
uncovered surface, as in flanges and the like, causes the loss of 
about one dollar per year in condensation of steam , and each square 
foot of uncovered surface represents the loss of nearly one-quarter 
of this amount. The principle of construction is to design the 
piping with the utmost simplicity possible ; without any double 
connections, put it up so that no accidents can happen to it. It 
is argued that this is impossible, but it is equally impossible to 
insure absolute immunity against " shut downs," of greater or 
less duration, by any amount of duplex connections, for even 
the blowing out of a single gasket can blow down a whole battery 
of boilers before a 12-inch valve can be closed and another 
opened. With the more extensive introduction of high-pressure 
valves and fittings, it is possible, by proper design, to reduce 
the'liability to accident very nearly to the point of absolute 
safety, and by the introduction of one or two extra valves, it is 
generally possible to divide the plant into sections, any one of 
which can, if occasion demands,' be operated independently. No 
fixed rules can be laid down and the line between absolute sim- 
plicity and necessary complexity must be drawn separately for 
each plant with due regard to the work it has to perform , but it 



HANDBOOK ON ENGINEERING. 



675 



should be remembered that the more simple a plant can be made 
to accomplish the work with absolute reliability, the greater the 
achievement in economy of first cost, and in availability and 
economy of operation. 




Piagram Showing Screwed Valve and Fittings 




■^ - ^rr::n^_j^ ;z:izi ^^}__^j [d^i ^i0 \ 




Piagram Showing Flanged Valve and Fittings 



CUTTING PIPE TO ORDER. 



In placing orders for pipe, a diagram should be made, accord- 
ing to above cuts. Great care should be taken in making a 
diagram for large pipe ; all measurements should be from centers. 
When flanged fittings are used, state if desired drilled, and if 
with bolts and gaskets complete. Also state if you desire the 



676 



HANDBOOK ON ENGINP^ERING. 



fittings made up tight, and mark such pieces at point joint is 
desired, on diagram. 



FEED=WATER REQUIRED BY SHALL ENGINES. 



Pressure of Steam 

in Boiler, by 

Gauge. 


Poun 

per 

Horsf 


ds of Water 
Effective 
-power per 
Hour. 


Pressure of Steam 

in Boiler, by 

Gauge. 


Pounds of Water 

per Effective 

Horse -power per 

Hour. 


10 






118 


60 






75 


15 






111 


70 






71 


20 






105 


80 






68 


25 






100 


90 






65 


30 






93 


100 






63 


40 






84 


120 






61 


50 






79 


160 






58 



HEATING FEED=WATER. 

Feed-water, as it comes from the wells or hydrants, has ordi- 
narily a temperature of from 35° in winter to from 60 to 70° in 
summer. Much fuel can be saved by heating this water by the 
exhaust steam, whose heat would otherwise be wasted. Until 
quite recently, only non-condensing engines utilized feed water 
heaters but lately they have been introduced with success between 
the cylinder and the air-pump in condensing engines. The 
saving in fuel due to heating feed-water is given on page 644. 



RATING BOILERS BY FEED=WATER. 

The rating of boilers has, since the Centennial Exposition in 
1876, been generally based on 30 pounds feed water per hour per 
horse-power. This is a fair average for good non-condensing engines 
forking under about 70 to 100 pounds pressure, But different 



HANDBOOK ON ENGINEERING. 



677 



pressures aud different rates of expansion change the require- 
ments for feed water. The following table gives Prof. R. H. 
Thurston's estimate of the steam consumption for the best classes 
of engines in common use when of moderate size and in good 
order : — 

WEIGHTS OF FEED WATER AND OF STEAM. 

NON-CONDENSING ENGINES. — R. H. T. 



Steam Pressure. 


Lbs. per H. P. 


per Hour 


•. — Ratio of Expansion. 


Atmos- 
phere. 


Lbs. per 
sq. Id. 


2 


3 


* 


r 


7 10 


3 


45 


40 


39 


40 


40 


42 


45 


4 


60 


35 


34 


36 


36 


38 


40 


5 


75 


30 


28 


27 


26 


30 


32 


6 


90 


28 


27 


26 


25 


27 


29 


7 


105 


26 


25 


24 


23 


25 


27 


8 


120 


25 


24 


23 


22 


22 


21 


10 


150 


24 


23 


22 


21 


20 


20 



CONDENSING ENGINES. 



2 


30 


30 


28 


28 


30 


35 


40 


3 


45 


28 


27 


27 


26 


28 


32 


4 


60 


27 


26 


25 


24 


25 


27 


5 


75 


26 


25 


25 


23 


22 


24 


6 


90 


26 


24 


24 


22 


21 


20 


8 


120 


25 


23 


23 


22 


21 


20 


10 


150 


25 


23 


22 


21 


20 


19 



Small engines having greater proportional losses in friction, in 
leaks, in radiation, etc., and besides receiving generally less care 



(w8 HANDBOOK ON ENGINEERING. 

in construction and running than larger ones, require more feed 
water (or steam) per hour. 

FEED-WATER HEATERS. 

Inattention to the temperature of feed water for boilers is en- 
tirely too common, as the saving in fuel that may be effected by 
thoroughly heating the feed water — by means of the exhaust 
steam in a properly constructed heater — would be immense, as 
may be seen from the following facts : A pound of feed water en- 
tering a steam boiler at a temperature of 50° Fahr., and evapo- 
rating into steam of 60 lbs. pressure, requires as much heat as 
would raise 1157 lbs. of water 1 degree. A pound of feed water 
raised from 50° Fahr. to 220° Fahr. requires 987 thermal units 
of heat, which if absorbed from exhaust steam passing through a 
heater, would be a saving of 15 per cent in fuel. Feed water at a 
temperature of 200^ Fahr., entering a boiler, as compared in point 
of economy, with feed water at 50°, would effect a saving of over 
13 per cent in fuel ; and with a well-constructed heater there ought 
to be no trouble in raising the feed water to a temperature of 212*^ 
Fahr. If we take the normal temperature of the feed water at 60', 
the temperature of the heated water at 212*^ and the boiler pressure 
at 20 lbs., the total heat imparted to the steam in one case is 
1192. 5« minus 60° == 1132.5° ; and in the other case, 1192. 5« 
minus 212° = 980.5°, the difference being 152°, or a saving of 
152/1132.5 = 13.4 per cent. Supposing the feed water to enter 
the boiler at a temperature of 32° Fahr., each pound of water will 
require about 1200 units of heat to convert it into steam, so that 
the boiler will evaporate between 6| and 7 J lbs. of water per 
pound of coal. The amount of heat required to convert a pound 
of water into steam varies with the pressure, as will be seen by 
the following table : — 



HANDBOOK ON ENGINEERING. 



()79 



TABLE SHOWING THE UNITS OF HEAT REQUIRED TO CONVERT ONE POUND 
OF WATER, AT THE TEMPERATURE OF 32° FAHR. , INTO STEAM AT 
DIFFERENT PRESSURES. 



Pressure of 
Steam in lbs. per 
Sq. In. by Gauge. 



Units of Heat. 



Pressure of 
Steam in lbs. per 
Sq. In. by Gauge. 



Units of Heat. 





1 


1,148 


110 


1,187 




10 


1,155 


120 


1,189 




20 


1,161 


130 


1,190 




30 


1,165 


140 


1,192 




40 


1,169 


150 


1,193 




50 


1,173 


160 


1,195 




60 


1,176 


170 


1,196 




70 


1,178 


180 


1,198 




80 


1,181 


190 


1,199 




90 


1,183 


200 


1,200 




100 


1,185 







If the feed water has any other temperature the heat necessary 
to convert it into steam can easily be computed. Suppose, for 
instance, that its temperature is 65^, and that it is to be converted 
into steam having a pressure of 80 lbs. per square inch. The 
difference between 65 and 32 is 33 ; and subtracting this from 
1181 (the number of units of heat required for feed water hav- 
ing a temperature of 32*^), the remainder, 1148, is the number of 
units for feed water with the given temperature. Yet it must be 
understood that any design of heater that offers such resistance 
to the free escape of the exhaust steam as to neutralize the gain 
that would otherwise be obtained from its use, ought to be 
avoided, as the loss occasioned by back pressure on the exhaust, 
in many instances, counteracts the advantages derived from the 
heating of the feed water. 



Feed-water heaters are a most important feature of a good 
steam plant. First, by utilizing the heat of the exhaust steam 



680 



HANDBOOK ON ENGINEERING. 



from the engine or waste gases in chimney, the feed water may be 
heated to about 210'' Fahr., with ease, before entering boilers, 
by this means saving fuel and increasing capacity of boiler. 
Second. By heating the water, the boilers are protected from 
serious and unequal strain, as the difference of temperature be- 
tween incoming water and outgoing steam may be kept about 1 10 
(210'^ to 320°). Third. Every heater must necessarily be a 
water purifier, as the mud and lime are eliminated, to some degree 
at least, before the water reaches the boiler, by heat. 
TABLE. 

SHOWING GAIN IN USE OF FEED WATER HEATER. PERCENTAGE OF 
HEAT REQUIRED TO HEAT WATER FOR DIFFERENT FEDD AND BOILILN 
TEMPERATURES^ AS COMPARED WITH A FEED AND BOILING TEM- 
PERATURE OF 212°. 



Boiling 


Initial Temperature of feed 


water. 






Point. 






































Fahr. 


32° 


50° 


68° 


86° 


104° 


122° 


140° 


158° 


176«> 


194° 


212° 


212 


1.19,1.17 


1.15 


1.13 


1.11 


1.10 


1.08 


1.06 


1.04 


1.02 


1.00 


230 


1.20 


1.18 


1.16 


1.14 


1.12 


1.10 


1.08 


1.06 


1.04 


1.02 


1.01 


248 


1.20 


1.18 


1.16 


1.14 


1.13 


1.11 


1.09 


1.07 


1.05 


1.03 


1.01 


266 


1.21 


1.19 


1.17 


1.15 


1.13 


1.11 


1.09 


1.07 


1.06 


1.04 


1.02 


284 


1.21 


1.20 


1.18 


1.16 


1.14 


1.12 


1.10 


1.08 


1.06 


1.04 


1.02 


302 


1.22 


1.20 


1.18 


1.16 


1.14 


1.12 


1.11 


1.09 


1.07 


1.05 


1.03 


320 


1.22 


1.21 


1.19 


1.17 


1.15 


1.13 


1.11 


1.09 


1.07 


1.05 


1.03 


338 


1.23 


1.21 


1.19 


1.17 


1.15 


1.14 


1.12 


1.10 


1.08 


1.06 


1.04 


356 


1.23 


1.22 


1.20 


1.18 


1.16 


1.14 


1.12 


1.10 


1.08 


1.06 


1.04 


374 


1.24 


1.22 


1.20 


1.18 


1.17 


1.15 


1.13 


1.11 


1.09 


1.07 


1.05 


392 


1.24 


1.23 


1.21 


1.19 


1.17 


1.15 


1.13 


1.11 


1.09 


1.07 


1.06 


410 


1.25 


1.23 


1.22 


1.20 


1.18 


1.16 


1.14 


1.12 


1.10 


1.08 


1.06 


428 


1.25 


1.24 


1.22 


1.20 


1.18 


1.16 


1.14 


1.12 


1.11 


1.09 


1.07 



There ai'e two distinct types of heaters in which heat is derived 
from exhaust steam. These are known as closed and open 
heaters. Each has its advantages and disadvantages. The 
closed heater is constructed so that the water is forced under pres- 



HANDBOOK ON ENGINEERING. 081 

sure through tubes or chambers surrounded by the exhaust steam, 
the heat being transmitted through the walls of the tubes and cham- 
bers. The open heater is a vessel in which the feed water comes 
into direct contact with the exhaust steam, by spraying or inter- 
mingling. The heated water is pumped hot into the boiler. 
The closed heater has the advantage of permitting the water to 
pass through the pump cold and in that state is easily handled. 
To pump hot water from an open heater requires special care in 
piping and packing the feed-pump. The closed heater, being a 
purifier (if any lime is present in water, a portion is bound to be 
precipitated by heat), should be cleaned, a job about as difficult 
as cleaning a boiler ; or blown out, which is never a satisfactory 
method. In the precipitation of lime by heat, carbonic acid gas 
is set free and chemists say that this gas in a nascent state (just 
being born) attacks iron and brass. Whatever the cause, experi- 
ence has demonstrated that ordinary wrought iron, steel and 
brass, corrode under this action. The open heater, being usually 
a large chamber, is accessible for cleaning out, and if made with 
ordinary care will last a long time. A leak in it is not a serious 
matter, while a leak in the closed heater means a waste of hot 
water into the exhaust pipe. The open heater has, at times, 
been the cause of serious mishaps. In it the steam and water 
mix ; with any stoppage in exit of feed-water, there is danger 
of flooding the cylinder of the steam engine through exhaust 
pipe, causing a wreck. The more modern forms of these heaters 
and the experience obtained in their use have reduced this 
difficulty to a minimum. 

WATER. 

Pure water at 62° F. weighs 62.355 pounds per cubic foot, or 
8i lbs. per U. S. gallon; 7.48 gallons equal 1 cu. ft. It takes 
30 lbs., or 3.6 gal. for each horse-power per hour. It would be 
difficult to get at the total daily horse-power of steam used in the 



(382 HANDBOOK ON ENGINEERING. 

U. S., but it reaches ioto the billions of gallons of feed water per 
day. The importance of knowing what impurities exist in most 
feed waters, how these act on a boiler and how they may be re- 
moved is, therefore, patent to every intelligent engineer. I give 
therefore, the thoughts of some prominent investigators on the 
subject. 

ProL Thurston says : — 

" Incrustation and sediment are deposited in boilers, the one 
by the precipitation of mineral or other salts previously held in 
solution in the feed-water, the other by the deposition of mineral 
insoluble matters, usually earths, carried into it in suspension or 
mechanical admixture. Occasionably also, vegetable matter of a 
glutinous nature is held in solution in the feed water, and, pre- 
cipitated by heat or concentration, covers the heating surfaces 
with a coating almost impermeable to heat, and hence, liable to 
cause an overheating that may be very dangerous to the struc- 
ture. A powdery mineral deposit sometimes met with is equally 
dangerous, and for the same reason. The animal and vege- 
table OILS AND GKEASES CARRIED OVER FROM THE CONDENSER OR 
FEED WATER HEATER ARE ALSO VERY LIKELY TO CAUSE TROUBLE. 

Only mineral oils should be permitted to be thus introduced, and 
that in minimum quantity. Both the efficiency and safety of the 
boiler are endangered by any of these deposits. 

" The amount of the foreign matter brought into the steam 
boiler is often enormously great. A boiler of 100 horse-power 
uses, as an average, probably a ton and a half of water per 
hour, or not far from 400 tons per month, steaming ten hours 
per day ; and even with the water as pure as the Croton at 
New York, receives 90 pounds of mineral matter, and from 
many spring waters a ton^ which must be either blown out or 
deposited. These impurities are usually either calcium carbon- 
ate or calcium sulphate, or a mixture ; the first is most com- 
mon on land, the second at sea. Organic matters often 



HANDBOOK ON ENGINEERING. ^)83 

harden these mineral scales and make them more difficult of 
removal. 

' ' The only positive and certain remedy for incrustation and 
sediment, once deposited, is periodical removal by mechanical 
means at sufficiently frequent intervals to insure against injury by 
too great accumulation. Between times, some good may be done 
by special expedients suited to the individual case. No one 
process and no one antidote will suffice for all cases. 

" Where carbonate of lime exists, sal-ammoniac may be used 
as a preventive of incrustation, a double decomposition occur- 
ring resulting in the production of ammonia carbonate and 
calcium chloride — both of which are soluble, and the first of 
which is volatile. The bicarbonate may be in part precipitated 
before use by heating to the boiling point, and thus breaking 
up the salt and precipitating the insoluble carbonate. Solutions 
of caustic lime and metallic zinc act in the same manner. 
Waters containing tannic acid and the acid juices of oak, 
sumach, logwood, hemlock, and other woods, are sometimes 
employed, but are apt to injure the iron of the boiler, as may 
acetic or other acid contained in the various saccharine matters 
often introduced into the boiler to prevent scale, and which 
also make the lime-sulphate scale more troublesome than when 
clean. Organic matter should never be used. 

' ' The sulphate scale is sometimes attacked by the carbonate of 
soda, the products being a soluble sodium sulphate and a pulver- 
ulent insoluble calcium carbonate, which settles to the bottom like 
other sediments and is easily washed off the heating surfaces. 
Barium chloride acts similarly, producing barium sulphate and 
calcium chloride. All the alkalies are used at times to reduce 
incrustations of calcium sulphate, as is pure crude petroleum, the 
tannate of soda and other chemicals. 

" The effect of incrustation and of deposits of various kinds, is 
to enormously reduce the conducting power of heating surfaces ; 



684 HANDBOOK ON ENGINEERING. 

SO much so, that the power, as well as the ecouomio efficiency of 
a boiler, may become very greatly reduced below that for which it 
is rated, and the supply of steam furnished by it may become 
wholly inadequate to the requirements of the case. 

"It is estimated that y^g of an inch (0.16 cm.) thickness of 
hard ' scale ' on the heating surface of a boiler will cause a waste 
of nearly one- eighth of its efficiency, and the waste increases as the 
square of its thickness. The boilers of steam vessels are 
peculiarly liable to injury from this cause where using salt water, 
and the introduction of the surface condenser has been thus 
brought about as a remedy. Land boilers are subject to incrus- 
tation by the carbonate and other salts of lime and by the deposit 
of sand or mud mechanically suspended in the feed- water. 

THE TEMPERATURE AND PRESSURE OF SATURATED 
STEAM. 

The accompanying diagram and explanation, taken from that 
excellent publication. The Locomotive ^ will be found much more 
convenient for reference than steam tables. The description says 
that one of the most fundamental and best known facts in steam 
engineering is that saturated steam has a certain definite tem- 
perature for each and every definite pressure ; and in all books 
on steam we find tables of corresjDonding temperatures and pres- 
sures, by the use of which we are enabled to find out what 
the temperature of the steam is when we know what the pres- 
sure is, and vice versa. For accurate work these tables are all 
right ; but when (as is usually the case) we do not need to 
know either the temperature or the pressure with any very 
great precision, a diagram which presents the facts directly to 
the eye is much more convenient. Such a diagram is presented 
herewith. On the left-hand side of each vertical line I have 
marked the pressures, and on the right-hand side of the same 
lines I have marked the corresponding temperatures. The pres- 



HANDBOOK ON ENGINEERING. 



685 






45— 



40—: 



—285' 



55- 



30- 



Z5- 



ZO- 



— Z80' ^^~ 



15 — 



too- 

Us -- 



-BS5 



-ZSO 



$5- 



$0- 



\—Z75' 
Z70' 
— 265' 

260' 
'■^255' 



80- 



75" 



70' 



-250' 65- 

-245' 

-240' eo- 



■ZSS 

^-zso' 

■US' 



55- 



-ZIS" Us -_ 



II 






-335* 



-330* 



-3Z5' 



(45—^ 



140— 



—360' 



135 — 



130 — 



-.—355 



-320' ,25— 



-315' 



-310' 



IZO- 



115- 



110 — 



— 305' 



-300 



105- 



Us 



/35- 



—385' 



/SO — 



/8S— 



- — 380' 



ISO— 



175— 



—350' ijqJI 



— 345' 



— 3W 



165- 



160 — 



155— 



lis 
150—^ 



-375' 



-370' 



gQMfARATIVf'; PIAQRAM SHOWING THE TEMPERATURE AN© PRESSURE 
QK SATURATED ^TEAM, 



686 HANDBOOK ON ENGINEERING. 

sures are all gauge pressures, that is, they represent the direct 
gauge reading or pressure above that of the atmosphere. The 
temperatures are on the Fahrenheit scale. The diagram is based 
upon Prof. Cecil H. Peabody's steam tables, and we have 
assumed that the average atmospheric pressure is 14.70 pounds 
per square inch. 

A few examples will make the use of the diagram clear: (1) 
What is the temperature of saturated steam when its pressure, 
above the atmosphere, is 75 pounds per square inch? Ans. We 
find 75 pounds on the left-hand side of the second vertical line, 
and looking on the other side of the line we see that the corre- 
sponding temperature is just a fraction of a degree less than 320 
degrees Fahr. (2) What is the temperature of saturated steam 
when its pressure, above the atmosphere, is 197 lbs. per square 
inch? Ans. We find 197 lbs. on the left-hand side of the last 
vertical line. It is not marked in figures, but 195 is so marked, 
and 197 is two divisions higher than 195. Looking opposite to 
197 we see that the corresponding temperature is about half way 
between 386 degrees and 387 degrees. Hence, we conclude that 
the temperature of saturated steam at the given pressure is about 
386i<*. (3) When the temperature of saturated steam is 227*^*, 
what is its pressure? Ans. We find 227*^ on the right-hand 
side of the first line, two divisions above 225« ; and looking 
opposite to it, we see that the gauge pressure corresponding to 
this temperature is almost exactly five pounds. (4) When the 
temperature of saturated steam is 363^, what is its pressure? 
Ans. We find 36 3° on the right-hand side of the third vertical 
line, three divisions above 360^, and looking on the other side of 
the vertical line, we see that the corresponding gauge pressure is 
about 1441 lbs. to the square inch. 

SOMETHING FOR NOTHING. 

In the first place, it should be remembered that in mechanics 
the measure of work done is the foot pound, a term which defines 



HANDBOOK ON ENGINEERING. 



687 



itself. A foot pound of work is the amount of energy required to 
lift one pound one foot high. A foot pound, therefore, is the 
product of force and distance, force being simply a push or a 
pull. A machine can be made to increase the acting force, as 
is seen in the case of a crane, where the weight lifted is much 
greater than the force applied at the handle by the operator. It 
is also possible to increase the distance moved by some part of a 
machine, but it must be done by applying a greater force as in 
the case of a steam engine, where the distance moved by the belt 
is greater than the space passed over by the piston, but the total 
pressure of the steam against the piston is greater than the 
effective pull exerted by the belt. 



Melting Points of Metals and Solids. 



Antimony 
Bismuth 


melts at 


Brass 
Cadmium 




Cast Iron 


l( 


Copper 


(C 


Glass 


ic 


Gold 


CI. 


Lead 


(C 


Ice 


(C 



Deg 


Falir. ' 




. 951 ■ 




. 476 




. 1900 




. 602 


. 1890 to 2160 




. 1890 




. 2377 




. 2250 




. 594 




, 32 







Deg. Fahr. 


Platinum melts at 


. ... 4680 


Potassium 


u 


... 135 


Saltpeter 


(C 


... 600 


Steel 


ii 


2340 to 2520 


Sulphur 




... 225 


Silver 


a 


. . . 1250 


Tin 


iC 


... 420 


Wrought Iron 


2700 to 2880 


Zinc 


"■ 


... 740 


Aluminum 


(C 


. . . 1260 



In both the crane and the steam engine, however, the applied 
force multiplied by the distance through which it moves in a given 
time, must be enough greater than the product of the force at the 
crane hook or the rim of the fly-wheel, and the distance through 



688 HANDBOOK ON ENGINEERING. 

which it moves to make up for the loss through friction in the 
machine itself. The foot pounds of work done by any machine 
whatever must always be less than the foot pounds put into the 
machine in the same length of time. A study of this principle 
and of the methods of applying it, is all that is necessary to 
enable one to decide upon the soundness of the claims made for 
any power multiplying device. A British Thermal Unit (B. T. 
U.) is the amount of heat required to raise the temperature of a 
pound of water 1° Fahr., and its dynamic value is 778 lbs. raised 
to a height of one foot. 

CHIMNEYS. 

Chimneys are required for two purposes : 1st, to carry off 
obnoxious gases ; 2d, to produce a draft, and so facilitate com- 
bustion. The first requires size, the second height. Each pound 
of coal burned yields from 13 to 30 pounds of gas, the volume of 
which varies with the temperature. The weight of gas to be car- 
ried off by a chimney, in a given time, depends on three things — 
size of chimney, velocity of flow and density of gas. But as the 
density decreases directly as the absolute temperature, while the 
velocity increases with a given height, nearly as the square root 
of the temperature, it follows that there is a temperature at which 
the weight of gas delivered is a maximum. This is about 550° 
above the surrounding air. Temperature, however, makes so 
little difference that at 550° above the quantity is only 4 per cent 
greater than at 300°. Therefore, height and area are the only 
elements necessary to consider in an ordinary chimney. The in- 
tensity of draft is, however, independent of the size, and depends 
upon the difference in weight of the outside and inside columns of 
air, which varies nearly as the i3roduct of the height into the 
difference of temperature. This is usually stated in an equiva- 
lent column of water, and may vary from to possibly 2 inches, 
^fter a height b^^ been reached to produce draft of sufficient 



HANDBOOK ON ENGINEERING. 



689 




690 HANDBOOK ON ENGINEERING. 

intensity to burn fine, hard coal, provided the area of the chimney 
is large enough, there seems no good mechanical reason for add- 
ing further to the height, whatever the size of the chimney 
required. Where cost is no consideration, there is no objection 
to building as high as one pleases ; but for the purely utilitarian 
purpose of steam-making, equally good results might be attained 
with a shorter chimney at much less cost. The intensity of draft 
required varies with the kind and condition of the fuel and the 
thickness of the fires. Wood requires the least, and fine coal or 
slack the most. To burn anthracite slack to advantage, a draft 
of 11 inch of water is necessary, which can be attained by a well- 
proportioned chimney 175 feet high. Generally, a much less 
height than 100 feet cannot be recommended for a boiler, as the 
lower grades of fuel cannot be burned as they should be with a 
shorter chimney. 

The proportioning of chimneys is very largely a matter of expe- 
rience and judgment. Various rules have been formulated for 
this purpose, but they all vary more or less. A chimney must 
have sufficient cross-section to easily carry off the products of 
combustion, and be high enough to produce sufficient draft for 
complete and rapid combustion. Where there is a choice between 
a high narrow stack and a lower wide one, the nature of the fuel 
should decide the matter ; as a rule, the taller stack is preferable. 
The amount of fuel to be burnt per square foot of grate per hour 
has been increasing in modern practice ; therefore, the old rules do 
not fit the case any more. Then again, it makes a difference how 
many boilers are to run into the same chimney. The heaviest 
work of the chimney is immediately after firing, since the friction 
through the fresh coal is greater and the temperature less then 
than some minutes later. But it would be bad practice to fire all 
boilers or all doors simultaneously. Hence, the second boiler 
does not require as much area as the first ; say, 75 per cent will 
do. After that there comes the additional consideration that as 



HANDBOOK ON ENGINEERING. 



691 




^§% 



692 



HANDBOOK ON ENGINEERING. 



the diameter of the stack increases, the friction in stack and 
breeching decreases rapidly. Therefore, for the third and each 
succeeding boiler, 50 per cent of the first area will suffice. But 
as more are added, the height should be increased, more espe- 
cially if the horizontal flue from boiler to stack increases in length, 
as it usually will. A good rule is to make the height 25 times 
the diameter, with possibly a gradual decrease in the ratio to 20 
times the diameter for the larger chimneys. Thus a 4-foot diame- 
ter would call for 100-feet height, and a 5-foot, for 120-feet, a 
G-foot for 140-feet, and a 10-foot for 200-feet heiorht. 



TABLE OF SIZES OF CHIMNEYS. 





Diameter and Nominal Horse Power. 


Ml 


20" 


26" 


30" 


34" 


36" 


40" 


44" 


50" 


54" 


58" 


60" 64" 72" 

1 i 


78" 


70 ft 


40 

50 


60 
75 


























80 ft. 


100 
120 


130 

150 


150 
175 


175 

200 


200 
225 
250 
















90 ft 


300 
340 
360 














100 ft 






375 
400 
425 


430 
455 
500 


500 
550 
600 


600 
650 
700 


750 
825 
900 


930 


110 ft. 














990 


120 ft. 
















1050 























IRON CHIMNEY STACKS. 

In many places iron stacks are preferred to brick chimneys, 
iron chimneys are bolted down to the base so as to require no 
stays. A good method of securing such bolts to the stack is 
shown in detail in the figure on page 693. Iron stacks require to be 
kept well painted to prevent rust, and generallj^, where not bolted 
down, as here shown, they need to be braced by rods or wires to 
surrounding objects. With four such braces attached to an 
angle iron ring at | tlie height of stack, and spreading laterally at 



HANDBOOK ON ENGINEERING. 



(i93 



least an equal distance, each brace should have an area in square 
inches equal to ^woo *^^ exposed area of stack (dia. x height) in 
feet. Stability or power to withstand the overturning force of 




Holding down Bolts and Lugs. 



the highest winds, requires a proportionate relation between the 
weight, height, breadth of base, and exposed area of the chimney. 
This relation is expressed in the equation 



(7- 



dh^ 



'^W. 



in which d equals the average breadth of the shaft ; h = its 
height ; b = the breadth of base — all in feet ; W = weight of 
CHIMNEY IN LBS., and C = Si coeflacient of wind pressure per 



894 



HANDBOOK ON ENGINEERING. 



square foot of area. This varies with the cross-section of the 
chimney, and = 56 for a square, 35 for an octagon and 28 for a 
round chimney. Thus a square chimney of average breadth of 
8 feet, 10 feet wide at base and 100 feet high, would require to 
weigh 56x8x100x10=448,000 lbs., to withstand any gale 
likely to be experienced. Brickwork weighs from 100 to 130 
lbs. per cubic foot; hence, such a chimney must average 13 
inches thick to be safe. A round stack could weigh half as 
much, or have less base. 

WEIGHT OF SHEET LAP RIVETED STEEL SMOKE STACKS, 
PER FOOTo 



THICKNESS. 



DIA. 


No 

18 


No. 
16 


No. 

14 

13 


No. 

12 

17 


No. 

10 

21 


No. 
8 

25^ 


31i 


37 


i" 
4 

42 


47 


52^ 


58 


63 


68i 


A" 

73^ 


78} 


i" 


12" 


8 


10 


84 


14" 


9i 


11^ 


15i 


20 


241 


291 


36} 


42 


48^ 


54^ 


62i 


67 


73^ 


79i 


85 


91 


97 


16" 


10: 


13 


n^ 


23 


28 


34 


42 


49 


56 


63 


70 


77 


84 


91 


98 


106 


112 


18" 


Hi 


14^ 


19i 


26 


314 


38i 


47 


55 


63 


71 


79 


86 


94 


102 


110 


118 


126 


20" 


13 


16 


22 


11 


35' 


42 


52 


60 


69 


78 


86 


95 


104 


113 


121 


131 


138 


22" 


14^ 


M 


24i 


38i 


46 


54 


63i 

68^ 


73 


82 


91 


99 


108 


118 


1^7 


137 


146 


24" 


i4 


26| 


34i 


42 


51 


59 


781 


88 


98 


108 


118 


128 


137 


147 


157 


26" 


16i 


21 


2S| 


37 


45i 


55i 


63 


73i 


84 


94 


105 


115 


126 


137 


147 


158 


168 


28" 


18 


III 


31 


40 


49 


59^ 


67 


78 


89i 


100 


111 


122 


134 


145 


156 


167 


179 


30" 




33 


tn 


52| 


63| 


71 


83 


95' 


106| 


118 


180 


142 


154 


166 


178 


190 


32" 




26i 


35 


56 


68 


75 


87i 


lOOh 


113 


125 


138 


150 


163 


175 


188 


201 


•6i" 




28* 


37 


48i 


59i 


72i 


80 


93 


106 


119 


132 


146 


160 


173 


186 


199 


212 


36" 




29 
31 


39 


51 


63 


76: 


85 


100 


114 


128 


143 


158 


173 


188 


202 


216 


230 


38" 




41i- 


53i 


66^ 


80 


90 


105 


120 


135 


151 


166 


182 


198 


213 


227 


242 


40" 




33 


43i 


56| 


70 


85 


94 


110 


126 


142 


158 


174 


191 


208 


224 


239 


254 


42" 




35 


45i 


59^ 


73^ 


S9i 


98 


115 


132 


149 


166 


183 


200 


•217 


234 


250 


266 


44" 




36i 


48 


62 


77 


93^ 


103 


121 


138 


155 


173 


191 


209 


227 


245 


262 


279 


46" 




38i 


50i 


65 


80i 


97i 


107 


126 


144 


162 


181 


199 


218 


237 


255 


273 


291 


48" 




40' 


52i 


68 


84 


102 


112 


131 


150 


169 


188 


208 


227 


247 


266 


284 


303 


80" 






54i 


71 


87^ 


106i 


116 


136 


156 


176 


195 


216 


236 


258 


277 


296 


316 


52" 






57 


74 


91 


IIO5 


121 


142 


162 


182 


203 


224 


245 


266 


287 


307 


328 


54" 








77 


944 


114i 


124 


147 


168 


189 


211 


233 


254 


276 


298 


319 


349 


56" 








80 


98 


119 


133 


158 


180 


202 


225 


248 


270 


294 


317 


340 


363 


68" 








83 


102 


123i 


137 


164 


186 


209 


232 


256 


280 


304 


327 


351 


375 


60" 








86 


106 


127i 


142 


169 


192 


215 


240 


264 


289 


314 


338 


362 


387 


62" 








89 


110 


131} 


146 


174 


198 


222 


247 


273 


298 


324 


349 


374 


400 


64" 








92 


114 


136 


151 


179 


204 


229 


255 


281 


307 


333 


359 


385 


412 



HANDBOOK ON ENGINEERING. 695 

CHAPTER XXIV. 
HORSE=POWER OF GEARS. 

To determine the horse-power which any gear-wheel will trans- 
mit, four facts are required to be known : — 

1st. The kind of wheel, whether spur, bevel, spur mortise, or 
bevel mortise. 2d. The pitch. 3d. The face. 4th. The velocity 
of pitch circle in feet per second. 

Generally, the fourth fact is not known. It can be found if 
the pitch diameter of the wheel in inches and the number of revo- 
lutions per minute are given, for it can be obtained from them by 
the following rule : — 

Rule* — Griven the pitch diameter in inches and the number of 
revolutions per minute ; to find the velocity of pitch line in feet 
per second. 

First, multiply the pitch diameter (in inches) by the number 
of revolutions per minute. Second, divide the product thus found 
by 230. The quotient is the velocity required. 

Example. — What is the velocity of the pitch circle of a 
gear-wheel in feet per second, the pitch diameter = 43 inches, 
the revolutions per minute = 125 ? 

43 X 125 divided by 230 = 23.4 feet per second. 

Table \ shows the greatest horse-power which different kinds 
of gears of 1-inch pitch and 1-inch face will safely transmit at 
various pitch-line velocities. To find the greatest horse-power 
which any other pitch and face will safely transmit, the following 
rule can be used : — 

Rule* — Given, the pitch (in inches), face (in inches), velocity 
of pitch circle (in feet per second) , and kind of gear ; to find the 
greatest horse-power that can be safely transmitted. 

First. Find the horse-power in Table 2, which the given kind 



()9(3 



HANDBOOK ON ENGINEERING. 



of wheel with 1-inch pitch aud 1-iiich face will transmit at the 
given velocity. Second. Multiply the pitch by the face. Third. 
Multiply the horse-power found by the product of pitch by face. 
The final product is the horse-power required. 

Example. — What is the greatest horse-power that a bevel- 
wheel, 43" pitch diameter, 2" pitch, (5" face, and 125 revolutions' 
per minute will safely transmit? 

From previous example, we have found the pitch-line velocity 
to be 23.4 feet per second, which is nearest to a velocity of 24 
feet per second in Table 1. 

First, the horse-power which a bevel wheel of 1" pitch and 1' 
face will transmit is (from table) at this velocity 4.931. 

Second, the product of pitch by face is 2 x 6 = 12. 

Third , 12x4.931 =^-59.17 horse-power . Answer . 

Whenever it is desirable to know about the average horse- 
power that any wheel will transmit, | or i of the results obtained 
by the rule above should be taken. 

TABLE 1. — TABLE SHOWING THE HORSE -POWER WHICH DIFFERENT 
KINDS OF GEAR WHEELS OF ONE INCH PITCH AND ONE INCH FACE 
WILL TRANSMIT AT VARIOUS VELOCITIES OF PITCH CIRCLE. 



1 


'^ 


3 


4 


5 


Velocity of 
pitch circle in 


Spur Wheels. 


Spur Mortise 
Wheels. 


Bevel Wheels. 


Bevel 
Mortise 


ft. per sec. 






Wheels. 


2 


1.338 


.647 


..938 


.647 


3 


1.756 


.971 


1.227 


.856 


6 


2.782 


1.76 


1.76 


1.363 


12 


4.43 


3.1 


3.1 


2.16 


18 


5.793 


4.058 


4.058 


2.847 


24 


7.052 


4.931 


4.931 


3.447 


30 


8.182 


5.727 


5.727 


4.036 


36 


9.163 


6.314 


6.414 


4.516 


42 


10.156 


7.102 


7.102 


4.963 


48 


10.083 


7.680 


7.680 


5.411 



HANDBOOK ON ENGINEERING. 



697 



Note. — When velocities are given, which are between these 
in Table, the horse-power can be found by interpolation. 

Thus, the horse-power for spur wheels at 14 feet velocity is 
found as follows : — 



nus 12 = 2\ 

" 12rr=6j 



14 minus 12 = 
18 



5.793 minus 4.43= 1.363. 



Then f of 1.363 = .454 and .454 + 4.43 = 4,884 horse-power. 



TABLE 2. —SHAFTING, — HORSEPOWER TRANSMITTED BY VARIOUS 
SHAFTS, AT 100 REVOLUilONS PER MINUTE UNDER VARIOUS CON- 
DITIONS. 



1 


2 3 


4 


1 


2 


3 


4 


Diameter 
of Shaft. 


Line 
Shafts. 


Shaft as 
a Prime 
Mover. 


Shafts 
Under 
Slight 
Bending 
Strain, 


Diameter 
of Shaft. 


Line 

Shafts. 


Shaft as 
a Prime 
Mover. 


Shafts 
Under 
Slight 
Bending 
Strain. 



if" 


.7 


.4 


1.3 i 


3- 


.^n 


40. 


20. 


80' 


ItV 


1.3 


.7 


2.6 


3- 


"f" 


49. 


25. 


97. 




2.4 


1.2 


4.7 


4- 


1^" 


70. 


35. 


139. 


111" 


3.8 


1.9 


7.6 


4J 


-|" 


96. 


48. 


192. 


1L|" 


5.8 


2.9 


11.5 


5- 


V 


126. 


64. 


256. 


2iV' 


8.3 


4.2 


16.6 


5- 


"f" 


167. 


84. 


33t. 


2V' 


11.5 


5.8 


23. 


6- 


t 


266. 


133. 


532. 


2^" 


15.5 


7.8 


31. 


V 


399. 


200. 


797. 


nr 


20. 


10. 


40. 


8J 


-l" 


570. 


285. 


1139. 


SiV 


26. 


13. 


51. 


9J 


r" 


783. 


392. 


1566. 


3^" 


33. 


17. 


65. 











This table states the horse-power that various sizes of shafts 
will safely transmit at 100 revolutions per minute under various 
conditions. 

Prime movers are those shafts in which the variation above 
and below the average horse-power transmitted is great, also 
where the transverse strain due to belts or heavy pulleys is large, 
such as jack-shafts, crank-shafts, etc. 



698 HANDBOOK ON ENGINEERING. 

WHEEL GEARING. 

The pitch line of a wheel is the circle upon which the pitch 
is measured, and it is the circumference by which the diameter, 
or the velocity of the wheel, is measured. The pitch is the arc 
of the circle of the pitch line, and is determined by the num- 
ber of teeth in the wheel. The true pitch (chordal), or that 
by which the dimensions of the tooth of a wheel are alone 
determined, is a straight line drawn from the centers of two 
contiguous teeth upon the pitch line. The line of centers is 
the line between the centers of two wheels. The radius of a 
wheel is the semi-diameter running to the periphery of a tooth. 
The pitch radius is the semi-diameter running to the pitch line. 
The length of a tooth is the distance from its base to its ex- 
tremity. The breadth of a tooth is the length of the face of 
wheel. The teeth of wheels should be as small and numerous 
as is consistent with strength. When a pinion is driven by 
a wheel, the number of teeth in the pinion should not be 
less than eight. When a wheel is driven by a pinion, the 
number of teeth in the pinion should not be less than ten. 
The number of teeth in a wheel should always be prime to the 
number of the pinion ; that is, the number of teeth in the 
wheel should not be divisible by the number of teeth in the 
pinion, without a remainder. This is in order to prevent the 
same teeth coming together so often as to cause an irregular 
wear of their faces. An odd tooth introduced into a wheel is 
termed a hunting-tooth or cog. 

TO COMPUTE THE PITCH OF A WHEEL. 

Rule* — Divide the circumference at the pitch-line by the num- 
ber of teeth. 

Example. — Awheel 40 in. in diameter, requires 75 teeth; 
what is its pitch ? 

3.1416x40 , .^.. . 
= 1.6766 in. 

75 



HANDBOOK ON ENGINEERING. 699 

TO COMPUTE THE CHORDAL PITCH. 

Rule» — Divide 180^ by the number of teeth, ascertain the sin. 
of the quotient, and multiply it by the diameter of the wheel. 

Example. — The number of teeth is 75 and the diameter 40 

in. ; what is the true pitch ? 

1 80 

t^^ = 2° 24' and sin. of 2« 24' = .04188, which x 40 = 1.6762 in. 
75 

TO COMPUTE THE DIAMETER OF A WHEEL. 

Rule^ — Multiply the number of teeth by the pitch, and divide 
the product by 3. 1416. 

Example. — The number of teeth in awheel is 75, and the 
pitch 1.675 in. ; what is the diameter of it? 
75 X 1.675 



3.1416 



. = 40 in. 



TO COMPUTE THE NUMBER OF TEETH IN A WHEEL. 

Rule. — Divide the circumference by the pitch. 

TO COMPUTE THE DIAMETER WHEN THE TRUE PITCH IS GIVEN. 

Rule. — Multiply the number of teeth in the wheel by the true 
pitch, and again by .3184. 

Example. — Take the elements of the preceding case. 
75 X 1.6752 X .3184 = 40 in. 

TO COMPUTE THE NUMBER OF TEETH IN A PINION OR FOLLOWER TO 
HAVE A GIVEN VELOCITY. 

Rule* — Multiply the velocity of the driver by its number of 
teeth, and divide the product by the velocity of the driven. 

Example. — The velocity of a driver is 16 revolutions, the 
number of its teeth 54, and the velocity of the pinion is 48 ; what 
is the number of its teeth ? 

, = 18 teeth. 

48 



700 HANDBOOK ON ENGINEERING. 

2. A wheel having 75 teeth is making 16 revokitious per min- 
ute. What is the number of teeth required in the pinion to make 
24 revolutions in the same time ? 
16x75 



24 



= 50 teeth. 



TO COMPUTE THE PROPORTIONAL RADIUS OF A WHEEL OR PINION. 

Rule* — Multiply the length of the line of centers by the num- 
ber of teeth in the wheel for the wheel, and in the pinion for the 
23inion, and divide by the number of teeth in both the wheel and 
the pinion. 

TO COMPUTE THE DIAMETER OF A PINION, WHEN THE DIAMETER OF 
THE WHEEL AND NUMBER OF TEETH IN THE WHEEL AND PINION 
ARE GIVEN. 

Rule» — Multiply the diameter of the wheel by the number of 
teeth in the pinion, and divide the product by the number of teeth 
in the wheel. 

Example. — The diameter of a wheel is 25 in., the number of 
its teeth 210, and the number of teeth in the pinion 30 ; what is 
the diameter of the pinion ? 

25x30 



210 



:3.57 in. 



TO COMPUTE THE CIRCUMFERENCE OF A WHEEL. 

Rule. — Multiply the number of teeth by their pitch. 

TO COMPUTE THE REVOLUTIONS OF A WHEEL OR PINION. 

Rule* — Multiply the diameter or circumference of the wheel or 
the number of its teeth, as the case may be, by the number of its 
revolutions, and divide the product by the diameter, circumfer- 
ence, or number of teeth in the pinion. 

Example. — A pinion 10 in. in diameter is driven by a wheel 



HANDBOOK ON ENGINEERING. 701 

2 ft. iu diameter, making 46 revolutioDS per minute ; what is the 
number of revohitions of the pinion ? 
2 X 12x46 



10 



110.4 revohitions. 



TO COMPUTE THE VELOCITY OF A PINION. 

Rule* — Divide the diameter, circumference or number of teeth 
in the driver, as the case may be. by the diameter, etc., of tlie 
pinion. 

WHEN THERE IS A SERIES OR TRAIN OF WHEELS AND PINIONS. 

Rule* — Divide the continued produet of the diameter, circum- 
ference, or number of teeth in the wheels by the continued 
product of the diameter, etc., of the pinions. 

Example. — If a wheel of 32 teeth drive a pinion of 10, upon 

the axis of which there is one of 30 teeth, driving a pinion of 8, 

what are the revolutions of the last? 

32 30 960 

Y^. X — = -^ =12 revolutions. 

Ex. 2, — The diameters of a train of w^heels are 6, 9, 9, 10 and 

12 in. ; of the pinions, Q^^., '6., 6, and 6 in. ; and the number of 

revolutions of the driving shaft or prime mover is 10 ; what are 

the revolutions of the last pinion ? 

6x9x9x10x12x10 583200 

/o revolutions. 



Q^C^^Q^^^^^i:^ 7776 

TO COMPUTE THE PROPORTION THAT THE VELOCITIES OF THE W^HEELS 
IN A TRAIN W^OULD BEAR TO QNE ANOTHER. 

Rule* — Subtract the less velocity from the greater, and divide 
the remainder by one less than the number of wheels in the train ; 
the quotient is the number, rising in arithmetical progression from 
the less to the greater velocity. 



702 HANDBOOK ON ENGINEERING. 

Example. — What should be the velocities of three wheels to 
produce 18 revolutions, the driver making 3 ? 

— = 7.5 = number to be added to velocity of the 
3 minus 1=2 

driver = 7.5 + 3 == 10.5 and 10.5 -|- 7.5 = 18 revolutions. 

Hence, 3, 10.5 and 18 are the velocities of the three wheels. 

GENERAL ILLUSTRATIONS. 

1. A wheel 96 inches in diameter, having 42 revolutions per 

minute, is to drive a shaft 75 revolutions per minute, what should 

be the diameter of the pinion ? 

96x42 .^ r-a • 
:= 53.76 m. 

75 

2. If a pinion is to make 20 revolutions per minute, required 
the diameter of another to make 58 revolutions in the same time. 
58 divided by 20 := 2.9 = the ratio of their diameters. Hence 
if one to make 20 revolutions is given a diameter of 30 in., the 
other will be 30 divided by 2.9 = 10.345 in. 

3. Required the diameter of a pinion to make 12i revolutions 

in the same time as one of 32 in. diameter making 26. 

32x26 .. ... 

66.56 m. 

12.5 

4. A shaft having 22 revolutions per minute, is to drive another 
shaft at the rate of 15, the distance between the two shafts upon 
the line of centers is 45 in. ; what should be the diameter of the 
wheels ? 

Then, 1st, 22 + 15 : 22 : : 45 : 26.75 == inches in the radius of 
the pinion. 

2d. 22 H- 15 : 15 : : 45 : 18.24 ^inches in the radius of the spur. 

5. A driving shaft, having 16 revolutions per minute, is to 
drive a shaft 81 revolutions per minute, the motion to be com- 
municated by two geared wheels and two pulleys, with an inter- 
mediate shaft ; the driving wheel is to contain 54 teeth, and the 



HANDBOOK ON ENGINEERING. 703 

driving pulley ujjou the driven shaft is to be 25 in. in diameter ; 
required the number of teeth in the driven wheel, and the diameter 
of the driven pulley. Let the driven wheel have a velocity of 
V 16x81=36 a mean proportional between the extreme veloci- 
ties 16 and 81. 

Then, 1st, 36 : 16 : : 54 : 24 = teeth in the driven wheel. 

2d. 81 : 36 : : 25 : 11.11 = inches diameter of the driven pulley. 

6. If, as in the preceding case, the whole number of revolutions 
of the driving shaft, the number of teeth in its wheel and the 
diameter of the pulley are given, what are the revolutions of the 
shafts ? 

Then, 1st, 18 : 16 : : 54 : 48 = revolutions of the intermediate 
shaft. 

2d. 15 : 48 : : 25 : 80 = revolutions of the driven shaft. 

TO COMPUTE THE DIAMETER OF A WHEEL FOR A GIVEN PITCH AND 
NUMBER OF TEETH. 

Rule* — Multiply the diameter in the following table for the 
number of teeth by the pitch, and the product will give the diam- 
eter at the pitch circle. 

Example. — What is the diameter of a wheel to contain 48 
teeth of 2.5 in. pitch? 

15.29x2.5 = 38.225 in. 

TO COMPUTE THE PITCH OF A WHEEL FOR A GIVEN DIAMETER AND 
NUMBER OF TEETH. 

Rule* — Divide the diameter of the wheel by the diameter in 
the table for the number of teeth, and the quotient will give the 
piitch. 

Example. — What is the pitch of a wheel when the diameter of 
it is 50.94 in., and the number of its teeth 80? 
50.94 
25:47==^ "^- 



704 



HANDBOOK ON ENGINEERING. 



PITCH OF WHEELS. 

A TABLE WHEREBY TO COMPUTE THE DIAMETER OF A WHEEL FOR A 
GIVEN PITCH, OR THE PITCH FOR A GIVEN DIAMETER. 

From 8 to 192 teeth. 



i 


1 

S 
a 

2.61 


o © 

6 

)^ 

45 


14.33 


i 

82 


£ 
26.11 




£ 

5 


i 

156 


2 

a 

5 

5 


8 


119 


37.88 


49.66 


9 


2.93 


46 


14.65 


83 


26.43 


120 


38.2 


157 


49.98 


10 


3.24 


47 


14.97 


84 


26.74 


121 


38.52 


158 


50.3 


11 


3.55 


48 


15.29 


85 


27.06 


122 


38.84 


159 


50.61 


12 


3.86 


49 


15.61 


86 


27.38 


123 


39.16 


160 


50.93 


13 


4.18 


50 


15.93 


87 


27.7 


124 


39.47 


161 


51.25 


14 


4.49 


51 


16.24 


88 


28.02 


125 


39.79 


162 


51.57 


15 


4.81 


52 


16.56 


89 


28.33 


126 


40.11 


163 


51.89 


16 


5.12 


53 


16.88 


90 


28.65 


127 


40.43 


164 


52.21 


17 


5.44 


64 


17.2 


91 


28.97 


128 


40.75 


165 


52.52 


18 


5.76 


55 


17.52 


92 


29.29 


129 


41.07 


166 


52.84 


19 


6.07 


56 


17.8 


93 


29.61 


130 


41.38 


167 


53.16 


20 


6.39 


57 


18.15 


94 


29.93 


131 


41.7 


168 


53.48 


21 


6.71 


58 


18.47 i 


95 


30.24 


132 


42.02 


169 


53.8 


22 


7.03 


59 


18.79 


9H 


30.56 


133 


42.34 


170 


54.12 


23 


7.34 


60 


19.11 


97 


30.88 


134 


42.66 


171 


54.43 


24 


7.66 


61 


19.42 


98 


31.2 


135 


42.98 


172 


54.75 


25 


7.98 


62 


19.74 1 


99 


31.52 


136 


43.29 


173 


55.07 


26 


8.3 


63 


20.06 1 


100 


31.84 


137 


43.61 


174 


55.39 


27 


8.61 


64 


20.38 : 


101 


32.15 


138 


43.93 


175 


55.71 


28 


8.93 


%b 


20-7 \ 


102 


32.47 


139 


44.25 


176 


56.02 


29 


9.25 


66 


21.02 


108 


32.79 


140 


44.57 


177 


56.34 


30 


9.57 


67 


21.33 


104 


33.11 


141 


44.88 


178 


56.66 


31 


9.88 


68 


21.65 


105 


33.43 


142 


45.2 


179 


56.98 


32 


10.2 


69 


21.97 


106 


33.74 


143 


45.52 


180 


57.23 


33 


10.52 


70 


22.29 


107 


84.06 


144 


45.84 


181 


57.62 


34 


10.84 


71 


22. 6i 


108 


34.38 


145 


46.16 


182 


57.93 


35 


11.16 


72 


22.92 


109 


34.7 


146 


46.48 


183 


58.25 


36 


11.47 


73 


23.24 


110 


35.02 


147 


46.79 


184 


58.57 


37 


11.79 


74 


23.56 


111 


35.34 


148 


47.11 


185 


58.89 


38 


12.11 


75 


23.88 


112 


35.65 


149 


47.43 


186 


59.21 


39 


12.43 


76 


24.2 


113 


85.97 


150 


47.75 


187 


59.53 


40 


12.74 


77 


24.62 


114 


36.29 


151 


48.07 


188 


59.84 


41 


13.06 


78 


24.83 


115 


36.61 


152 


48.39 


189 


60.16 


42 


13.38 


79 


25.15 


116 


36.93 


153 


48.7 


190 


60.48 


43 


13.7 


80 


25.47 


117 


37.25 


154 


49.02 


191 


60.81 


44 


14.02 


81 


25.79 


118 


37 . 56 


155 


49.34 


192 


61.13 



HANDBOOK ON ENGINEERING. 



705 



TO COMPUTE THE STRESS THAT MAT BE BORNE BY A TOOTH. 

Rule^ — Multiply the value of the material of the tooth to re- 
sist transverse strain, as estimated for this character of stress, by 
the breadth and square of its depth, and divide the product by 
the extreme length of it in the decimal of a foot. 

TO COMPUTE THE NUMBER OF TEETH OF A WHEEL FOR A GIVEN 
DIAMETER AND PITCH. 

Rule* — Divide the diameter by the pitch , and opposite to the 
quotient in the preceding table is given the number of teeth. 

TEETH OF WHEELS. 

EpicycIoidaL — In order that the teeth of the wheels and pin- 
ions should work evenly and without unnecessary rubbing fric- 
tion, the face (from pitch line to top) of the outline should be 
determined by an epicycloidal curve, and the flank (from pitch 
line to base) by an hypocycloidal. When the generating circle is 
equal to half the diameter of the pitch circle, the hypocycloid de- 
scribed by it is a straight diametrical line, and consequently the 
outline of a flank is a right line and radial to the center of the 
wheel. If a like generating circle is used to describe face of a 
tooth of other wheel or pinion respectively, the wheel and pinion 
will operate evenly. 

Involute* — Teeth of two wheels will work truly together when 
surfaces of their face is an involute ; and that two such wheels 
should work truly, the circles from which the involute lines for 
each wheel are generated must be concentric with the wheels, 
with diameters in the same ratio as those of the wheels. 

Curves of teeth* — In the pattern shop, the curves of epicy- 
cloidal or involute teeth are defined by rolling a template of the 
generating circle on a template corresponding to the pitch line, 
a scriber on the periphery of the template being used to define 



706 



HANDBOOK ON ENGINEERING. 



the curve. Least number of teeth that can be employed in pin- 
ions having teeth of following classes, are : involute, 25 ; 
epicycloidal, 12 ; staves or pins, 6. 



CONSTRUCTION OF QEARINQ. 

If the dimensions of two wheels are determined, as well as 
the size of the teeth and spaces, the wheel is drawn as shown 
in figure. The starting- 
point for the division of 
the wheels is where the 
two pitch circles meet 
in A. It is advisable 
to determine the exact 
diameters of the wheels 
by calculation, if the 
difference between 
them is remarkable ; for 
any division upon two 
circles of unequal size 
by means of a divider, 
is incorrect, because the latter measures the chord instead of the 
arc. From the point A we construct the epicycloid C, by rolling 
the circle A upon B, as its base line. That short piece of the epi- 
cycloid, from the pitch line to the face of the tooth, is the curva- 
ture for that part of the tooth and the wheel B. This curvature 
obtained for one side of the tooth, serves for both sides of it, and 
also for all the teeth in the wheel. The lower part of the tooth, 
or that inside the pitch -line, is immaterial to the working of the 
wheel; this may be a straight line, as shown by the dotted lines 
which are in the direction of the diameters, or may be a curved 
line, as is seen in the wheel A. This line must be so formed as 
not to touch the upper or curved part of the tooth. The root of 




HANDBOOK ON ENGINEERING. 



707 



the tooth, or that part of it which is connected with the rim of the 
wheel, is the weakest part of the tooth, and may be strengthened 
by filling the angles at the corners. The curvature for the teeth 
in the wheel A is found in a similar manner to that of B. The 
pitch circle A serves now as a base line, and the circle B is rolled 
upon it, to obtain the circle D. This line forms the curvature for 
the teeth of A, and serves for all the teeth in A — also for both 
sides of the teeth. In most practical cases the curvature of the 
teeth is described as a part of a circle, drawn from the center of 
the next tooth, or from a point more or less above or below that 
center, or the radius greater or less in strength than the pitch of 
the wheel. Such circles are never correct curves, and no rule can 
be established by which their size and center meets the form of 
the epicycloid. 

BEVEL W^HEELS. 

If the lines C A and B C represent the prolonged axes, which 
are to revolve with different or similar velocities, the position and 

sizes of the wheels for 
driving these axes are 
determined by the dis- 
tance of the wheels from 
the point 0. The diame- 
ters of the wheels are as 
the angles a and b and 
inversely as the number 
of revolutions. These 
angles are, therefore, to 
be determined before the 
wheels can be drawn. 
By measuring the distances from C to the hne E^ or from C to 
F, the sizes of the wheels are determined. These lines E^ F and 
D F, are the diameters for the pitch lines ; from them the form 




708 



HANDBOOK ON ENGINEERING. 



of the tooth is described on the beveled face of the wheel. If 
the form of the tooth is described on the largest circle of the 
wheel, all the lines from this face run to the point O, so that when 
the wheel revolves around its axis, all the lines from the teeth 
concentrate in the point C, and form a perfect cone. Curvature, 
thickness, length and spaces are here calculated as on face 
wheels ; the thickness is measured in the middle of the width of 
the wheel. 

WOKM-SCREW. 

If a single screw A works in a toothed wheel, each revolution 
of the screw will turn the wheel one cog ; if the screw is formed 
of more than one thread, a corresponding number of teeth will be 
moved by each revolution. 
With the increase of the 
number of threads, the side 
motion of the wheel and 
screw is . accelerated ; and 
when the threads and num- 
ber of teeth are equal, an 
angle of 45« is required for 
teeth and thread, provided 
their diameters also are 
equal. This motion causes 
a great deal of friction and 
it is only resorted to where no other means can be employed to 
produce the required motion. In small machinery, the worm is 
frequently made use of to produce a uniform, uninterrupted 
motion ; the screw, in such cases, is made of hardened steel and 
the teeth of the wheel are cut by the screw which is to work in 
the wheel. If the form of the teeth in the wheel is not curved 
and its face is concave so as to fit the thread in all points, the 
screw will touch the teeth but in one point and cause them to be 
liable to breakage. 




HANDBOOK ON ENGINEERING. 709 

PKOPOKTIONS OF TEETH OF WHEELS. 

Tooths — In computiDg the dimensions of a tooth, it is to be 
considered as a beam fixed at one end, the weight suspended 
from the other, or face of the beam ; and it is essential to con- 
sider the element of velocity, as its stress in operation, at high 
velocity with irregular action, is increased thereby. The dimen- 
sions of a tooth should be much greater than is necessary to resist 
the direct stress upon it, as but one tooth is j^roportioned to bear 
the whole stress upon the wheel, although two or more are 
actually in contact at all times ; but this requirement is in 
consequence of the great wear to which a tooth is subjected? 
the shocks it is liable to from lost motion when so worn as to 
reduce its depth and uniformity of bearing, and the risk of the 
breaking of a tooth from a defect. A tooth running at a low 
velocity may be materially reduced in its dimensions comjjared 
with one running at high velocity and with a like stress. The 
result of operations with toothed wheels, for a long period of 
time, has determined that a tooth with a pitch of 3 inches and a 
breadth 7.5 inches will transmit, at a velocit}^ of 6.66 feet per 
second, the jjower of 59.16 horses. 

TO COMPUTE THE DEPTH OF A CAST-IKON TOOTH. 

1. When the stress is given. 

Rule* — Extract the square root of the stress, and multiply it 
by .02. 

Example. — The stress to be borne by a tooth is 4886 lbs. ; 
what should be its depth? 

1/4886 X .02 = 1.4 in. 

2. When the horse-power is given. 

Rule* — Extract the square-root of the quotient of the horse- 
power divided by the velocity in feet per second, and multiply it 
by .466. 



710 HANDBOOK ON ENGINEERING. 

Example. — The horse-power to be transmitted by a tooth is 
60, and the velocity of it at its pitch-line is 6.66 feet per second ; 
what should be the depth of the tooth ? 
~60" 



^ 



X .466 = 1.398 in. 



TO COMPUTE THE HORSE-POWEK OF A TOOTH. 

Rule* — Multiply the pressure at the pitch-line by its velocity 
in feet per minute, and divide the product by 33,000. 

CALCULATING SPEED W^HEN TIME IS KOT TAKEN INTO ACCOUNT. 

Rule* — Divide the greater diameter, or number of teeth, 
by the lesser diameter or number of teeth, and the quotient is 
the number of revolutions the lesser will make, for one of the 
greater. 

Example. — How many revolutions will a pinion of 20 teeth 
make, for 1 of a wheel with 125? 

125 divided by 20 = 6.25 or 61 revolutions. 

To find the number of revolutions of the last to one of the first, 
in a train of wheels and pinions : — 

Rule* — Divide the product of all the teeth in the driving by 
the product of all the teeth in the driven ; and the quotient equals 
the ratio of velocity required. 

Example 1. — Required the ratio of velocity of the last, to 1 

of the first, in the following train of wheels and pinions, viz. : 

pinions driving — the first of which contains 10 teeth, the second 

15, and third 18. Wheels driven, first teeth 15, second 25, 

10xl5x 18 
and third 32. ^^ ^p. — 709 =" -225 of a revolution the wheel 

will make to one of the pinion. 

Example 2. — A wheel of 42 teeth giving motion to 1 of 12, 
on which shaft is a pulley of 21 inches diameter, driving 1 of 6 ; 



HANDBOOK ON ENGINEERING. 711 

required the number of revolutions of the last pulley to 1 of the 

42x21 

first wheel. 77^ ^= 12.25 or 121 revolutions. 

12 X 6 * 

Note. — Where increase or decrease of velocity is required to 

be communicated by wheel- work, it has been demonstrated that 

the number of teeth on each j)inion should not be less than 1 to 

6 of its wheel, unless there be some other important reason for a 

higher ratio. 

WHEN TIME MUST BE REGARDED. 

Rule* — Multiply the diameter or number of teeth in the driver 
by its velocity in any given time, and divide the product by the 
required velocity of the driven ; the quotient equals the number 
of teeth or diameter of the driven, to produce the velocity 
required. 

Example 1. — If a wheel containing 84 teeth makes 20 revolu- 
tions per minute, how many must another contain, to work in 
contact, and make 60 revolutions in the same time: 
80x20 divided by 60 =27 teeth. 

Example 2. — From a shaft making 45 revolutions per minute 
and with a pinion 9 inches diameter at the pitch-line, I wish 
to transmit motion at 15 revolutions per minute ; what, at the 
pitcli-line, must be the diameter of the wheel? 

45x9 divided by 15 = 27 inches. 

Examples. — Required the diameter of a pulley to make 16 
revolutions in the same time as one of 24 inches making 36. 
24x 36 divided by 16 = 54 inches. 

The distance between the centers, and the velocities of two wheels 
being given, to find their proper diameters : — 

Rule* — Divide the greatest velocity by the least; the quo- 
tient is the ratio of diameter the wheels must bear to each other. 
Hence, divide the distance between the centers by the ratio + 1 ; 
the quotient equals the radius of the smaller wheel ; and subtract 



712 HANDBOOK ON ENGINEERING. 

the radius thus obtained from the distance between the centers ; 
the remainder equals the radius of the other. 

Example. — The distance of two shafts from center to center 
is 50 in. and the velocity of the one 25 revolutions per minute, 
the other is to make 80 at the same time ; the proper diameters 
of the wheels at the pitch line are required. 

80 divided by 25 = 3.2, ratio of velocity, and 50 divided by 
3.2+ 1 = 11.9, the radius of the smaller wheel ; then 50 minus 
11.9 =38.1, radius of larger ; their diameters are 11.9x2 = 23.8 
and 38.1x2 = 76.2 in. 

To obtain or diminish an accumulated velocity by means of 
wheels and j)inions, or wheels, pinions and pulleys, it is necessary 
that a proportional ratio of velocity should exist, and which is 
thus attained ; multiply the given and required velocities together ; 
and the square root of the product is the mean or proportionate 
.velocity. 

Example. — Let the given velocity of a wheel containing 54 
teeth equal 16 revolutions per minute, and the given diameter of 
an intermediate pulley equal 25 in., to obtain a velocity of 81 
revolutions in a machine ; required the number of teeth in the 
intermediate wheel and diameter of the last pulley. 

V 81x16 = 36 mean velocity ; 54 x 16 divided by 36 = 24 
teeth, and 25x36 divided by 81 = 11.1 in., diameter of pulley. 

TABLE OF THE WEIGHT OF A SQUARE FOOT OF SHEET IKON IN 
POUNDS AVOIRDUPOIS. 

No. 1 is -fQ of an inch ; No. 4, i ; No. 11, J, etc. 
No. on wire gauge, 12 3 4 5 6 7 8 9 10 11 12 



Poundsavoir., 12.5 12 11 10 9 


8 7.5 7 


6 5.68 5 4.62 


No. on wire gauge, 13 14 15 16 17 


18 19 


20 21 22 



Poundsavoir., 4.31 4 3.95 3 2.5 2.18 1.93 1.62 1.5 1.37 



HANDBOOK ON ENGINEERING. 713 

SCREW-CUTTING. 

In a lathe properly adapted, screws to any degree of j)itch, or 
number of threads in a given length, may be cut by means of a 
leading screw of any given pitch, accompanied with change wheels 
and pinions ; coarse pitches being effected generally by means of 
one wheel and one pinion with a carrier, or intermediate wheel, 
which cause no variation or change of motion to take place ; hence, 
the following : — 

Rule* — Divide the number of threads in a given length of the 
screw which is to be cut, by the number of threads in the same 
length of the leading screw attached to the lathe, and the quotient 
is the ratio that the wheel on the end of the screw must bear to 
that on the end of the lathe spindle. 

Example. — Let it be required to cut a screw with 5 threads 
in an inch, the leading screw being of i inch pitch, or containing 
2 threads in an inch ; what must be the ratio of wheels applied ? 

5 divided by 2 = 2.5, the ratio they must bear to each other. 
Then suppose a pinion of 40 teeth be fixed upon for the spindle ; 
40 X 2.5 ^ 100 teeth for the wheel on the end of the screw. 

But screws of a greater degree of fineness than about 8 threads 
in an inch are more conveniently cut by an additional w^heel and 
pinion, because of the proper degree of velocity being more 
effectively attained, and these, on account of revolving upon a 
stud, are commonly designated the stud- wheels, or stud-wheel 
and pinion ; but the mode of calculation and ratio of screw are the 
same as in the preceding rule. Hence, all that is further neces- 
sary is to fix upon any three wheels at pleasure, as those for the 
spindle and stud-w^heels ; then multiply the number of teeth in 
the spindle-wheel by the ratio of the screw and by the number of 
teeth in that wheel or pinion which is in contact with the wheel 
on the end of the screw ; divide the product by the stud-wheel in 
contact with the spindle-wheel, and the quotient is the number of 
teeth required in the wheel on the end of the leading screw. 



714 



HANDBOOK ON ENGINEERING. 



Example. — Suppose a screw is required to be cut containing 

25 threads in an inch, and the leading screw, as before, having 

two threads in an inch, and that a wheel of 60 teeth is fixed upon 

for the end of the spindle, 20 for the pinion in contact with the 

screw-wheel, and 100 for that in contact with the wheel on the 

end of the spindle ; required the number of teeth in the wheel for 

the end of the leading screw. 

rtK T • 1 1 u n M^ ^ -, 60 X 12.5 X 20 

25 divided by 2 = 12.5, and -^- ^ 150 teeth. 

Or suppose the spindle and screw wheels to be those fixed upon, 
also any one of the stud-wheels, to find the number of teeth in the 
other. 



150 X 100 



60x12.5 



=r=20 teeth, or 



60x 12.5 X 20 
l50 ' 



: 100 teeth. 



Transmission of Power by Manilla Rope, 
power Transmitted. 



Horse- 



Feet per minute .... 


1000 


1500 


2000 


2500 


3000 


3500 


4000 


4500 


5000 


Diameter of Rope . 


. 1 


11 


2% 


3^ 


4i 


5^ 


6* 


7 


8 


9 


CC iC 


. 1 


H 


^l 


H 


8 


10 


11 


13 


15 


16 


<( CI 


. H 


H 


n. 


m 


13 


15 


18 


20 


23 


26 


a C( 


• H 


n 


11 


15 


18 


22 


26 


30 


34 


37 


a a 


. U 


10 


15 


20 


25 


30 


35 


40 


45 


50 


U (( 


2 


13 


iH 


26 


33 


39 


46 


52 


59 


65 



Decimal Equivalents of One Foot by Inches. 



k 


^ 


1 


1 


2 


0208 


.0417 


.0626 


.0833 


.1667 


6 


7 


8 


9 


10 


5000 


.5833 


.6667 


.7510 


.8383 



11 : 12 
.9167 I 1.000 



HANDBOOK ON P^NGINEERTNG. 



715 



TABLE OF TRANSMISSION OF POWER BY 
WIRE ROPES. 

This table is based upon scientific calculations, careful observations 
and experience, and can be relied upon when the distance exceeds 100 
feet. We also find by experience that it is best to run the Wire Rope 
Transmission at the medium number of revolutions indicated in the table, 
as it makes the best and smoothest runninii transmission. If more 
power is needed than is indicated at 80 to 100 revolutions, choose a 
larger diameter of sheave. 



Diameter of 
Sheave in ft. 


1 

i Number of 
g Revolutions. 

j 


o 

si 

i 


Horse- 
Power. 


W 

Q.5 


a^ 


II 

5 




3 


3 


7 


140 


A 


35 


3 


100 


1 


3^ 


8 


80 


1 


26 


3 


120 


1 


4 


8 


100 


1 


32 


3 


140 


1 


4i 


8 


120 


1 


39 


i 


80 


f 


4 


8 


140 


1 


45 


4 


100 


f 


5 


9 


80 


{a 1 


\ 47 
] 48 


4 


120 


f 


6 


9 


100 


{a 1 


\ 58 
/ 60 


4 


140 


f 


7 


9 


120 


{At 


\ 69 
/ 73 


5 


30 


fe- 


9 


9 


140 


{At 


\ 82 
1 84 


5 


100 


-h 


11 


10 


80 


{l H 


\ 64 

/ 68 


5 


120 


-h 


13 


10 


100 


{IH 


\ 80 

1 85 


5 


140 


-h- 


15 


10 


120 


{ 1 H 


\ 96 

;io2 


6 


80 


h 


14 


10 


140 


{lii 


1112 
(119 


6 


100 


h 


17 


12 


80 


{hi 


\ 93 
/ 99 


6 


120 


h 


20 


12 


100 


{hi 


\116 
h24 


6 


140 


h 


23 


12 


120 


{hi 


1140 
il49 


7 


80 


A 


20 


12 


120 


I 


173 


7 


100 


A 


25 


14 


80 


{i U 


1141 

1148 


7 


120 


A 


30 


14 


100 


{i u 


\176 
1185 



716 HANDBOOK ON ENGINEERING. 



CHAPTER XXV. 
ELECTRIC ELEVATORS. 

In factories, warehouses and business buildings, freight, and in 
some instances passenger elevators, are operated by machines 
that are arranged to be driven by a belt. Such machines are 
variously called belted elevators, factory elevators and sometimes 
warehouse elevators. 

In factories where there is a line of shafting kept running 
continuously, they are driven from it. As a rule the elevator 
machine is driven from a countershaft which latter is belted to 
the line shaft. Very often the elevator machine is driven 
directly from the line shaft. As the line shaft runs always in the 
same direction, the only way in which the elevator machine can 
be made to run in both directions is by the use of two belts, one 
open and the other crossed, .or some form of gearing that will 
accomplish the same result. The common practice is to use 
double belts. Either one of these belts can be made to drive by 
using friction clutches, or by having tight and loose pulleys, and 
a belt shifter. The latter arrangement is the most common. 

In buildings where there is no line of shafting, power for oper- 
ating the elevator machine must be derived from some kind of 
motor installed expressly for the purpose. Nowadays electric 
motors are very extensively used for this purpose, and the com- 
bination of an elevator machine and an electric motor to drive it is 
very generally called an electric elevator, although in reality it is not 
such, but simply a belted elevator machine driven by an electric 
motor. It has become so common, however, to call such com- 
binations electric elevators, that true electric elevators are generally 
designated as " direct connected electric elevators.** 



HANDBOOK ON ENGINEERING. 717 

The fitst impression would be that in the combination of a 
belted elevator machine, and an electric motor to drive it, as the 
motor simply furnishes the power to set the machine in motion, 
there can be nothing about the combination that requires any 
special elucidation. Such a conclusion, however, would not be 
correct, for there are several ways in which the combination can 
be arranged, and in what follows I propose to explain these 
several combinations, pointing out the important features of 
each. 

The simplest way in which a motor can be installed to drive 
an elevator, is to arrange it so as to drive the counter shaft con- 
tinuously, in which case the elevator is stopped and started by 
throwing the belts on the tight or the loose pulley. Although 
this is a very simple arrangement, it is not desirable unless the 
elevator is kept in service all the time. In buildings where the 
elevator is used only at intervals, a great amount of power is 
wasted if the shafting is kept running all the time ; hence it is 
desirable to arrange the motor so that it can be stopped when the 
elevator is stopped, and started whenever the elevator is to be 
used. 

If the motor is arranged so as to run all the time, it is provided 
with a simple motor-starting switch, the same as is used for any 
motor installed to operate machinery of any kind. If the motor 
is started and stopped whenever the elevator is started and stopped, 
it is necessary to provide a motor-starter that can be operated 
from the elevator car. A very common way of arranging a motor 
to start and stop with the elevator is illustrated in the diagram 
(Fig. 1). 

In this diagram the elevator car is shown at C, with the lifting 
ropes running over the sheave F at the top of the elevator 
shaft, and then down and around the drum A of the elevator 
machine. This drum is driven by means of screw gearing, as a 
rule, with driving pulleys on the screw shaft as shown at B The 



718 



HANDBOOK ON ENGINEERING. 



iriving motor is shown at M^ and the counter-shaft to which it is 
belted is at D. In this arrangement the elevator machine is pro- 
vided with a tight center pulley and loose pulleys on the two sides. 
The belts are shown on the loose pulleys 5 one being open and the 




other being crossed » The countershaft carries a drum wide 
enough to allow for the side movement of the belts when one or 
the other is shifted upon the tight center pulley b}^ the belt shifter 
s. To operate the elevator car, a hand rope is provided which 



HANDBOOK ON ENGINEERING. 719 

runs up the elevator shaft at one side of the car from bottom to 
top of building. This rope is shown in the diagram at Z, and 
runs around two small sheaves a a. The lower one of these sheaves 
is provided with a crank pin which moves the connecting rod 6, 
and thus rocks the lever r, and thereby moves the belt shifter s. 
To cause the car to ascend the hand rope I is pulled down, and 
to make the car descend, the hand rope is pulled up. As will be 
seen from this explanation, the lower sheave a will rotate in one 
direction when the hand rope is pulled to make the car go up, and 
in the opposite direction when the rope is pulled to make the car 
run down. In the diagram, sheave a is shown in the stop posi- 
tion, therefore when the hand rope is pulled down so as to make 
the car run up, the sheave will turn in a direction opposite to the 
movement of the hands of a clock, and thus the belt shifter will 
be moved to the right, and the open belt will be run onto the tight 
center pulley. If the hand rope is pulled up sheave a will rotate 
in the direction of the hands of a clock, and the belt shifter will 
move toward the left and thus shift the crossed belt onto the tight 
pulley. The rope _p is a stop rope and is connected with the two 
sides of the hand rope in the manner shown, so that when the car 
is running in either direction, if j? is pulled hard it will bring I to 
the position shown in the diagram, and thus stop the car. This 
rope can be dispensed with, but the objection is that in pulling 
the hand rope I to stop the car it may be pulled too far and then 
the car will not only be stopped but it will be caused to run in 
the opposite direction. 

The motor starting switch is shown at E, the line wires being 
connected with the two top binding posts. The lever c c is in one 
piece and is independent of lever e, but both swing around the 
same pivot. At m, a dash pot is provided which acts to prevent 
the too rapid movement of lever e. As will be noticed, lever c 
has a projection which holds lever e up. The operation of this 
motor starter is as follows : When the hand rope I is pulled in 



720 HANDBOOK ON ENGINEERING. 

either direction, the rope h draws lever c towards the left and 
causes it to make contact with the switch jaw j. In this way the 
current from the upper binding post which is connected with J 
through wire ^, passes to lever e, and thus to the starting resist- 
ance, which is indicated by the dotted lines t, to binding post yfc, 
from where it goes to the motor armature through wire d, and re- 
turns through the other wire d to the upper binding post at the 
right side, which is connected with the opposite side of the main 
line, thus completing the circuit. The field current branches off 
from the upper end of the starting resistance i and reaches the 
field coils through wire /, and through the lower wire / reaches 
the return armature wire d and thus the opposite side of the cir- 
cuit. When the rope h pulls lever c over toward the left, the lever 
e does not follow it, as it is held up by the dash pot m. The 
weight on the end of e gradually overcomes the resistance of the 
dash pot, and thus causes lever e to move downward slowly. The 
velocity at which e moves downward is graduated by adjusting 
the opening in the dash pot through which the oil flows. 

From the foregoing it will be seen that the starter E is made so 
as to accomplish automatically just what a man accomplishes 
when he moves the lever of an ordinary motor-starter ; that is, it 
first closes the circuit through the motor, b}^ bringing lever c into 
contact with J; and then allows lever e to move slowly so as 
to cut the resistance i out of the armature circuit gradually. 
When the elevator is stopped, by pulling the hand rope I to the 
stop position, the rope h slacks up and then the weight on the end 
of lever c causes it to descend, and thus return lever e to the posi- 
tion shown in the diagram, and also to break the circuit between 
c and j. 

The elevator machine A is provided with a brake which is 
actuated by the belt shifter s, so that when the belts are shifted 
upon the side pulleys, as shown in the diagram, the brake is put 
on, and thus the machine is stopped. As soon as the belt shifter 



HANDBOOK ON ENGINEERING. 721 

is moved to set the car in motion the brake is raised, so as to 
allow the machine to run free. 

This arrangement is used very extensively, although the motor- 
starting switch is not always made in strict accordance with the 
one shown at E. In fact, there are a great many different designs 
on the market, but they all accomplish the same result, although 
the means employed may be very different. 

Although it is very advantageous to have the motor arranged 
as in Fig. 1, so that it may be stopped and started together with 
the elevator, there is one objection to it which is sometimes re- 
garded as serious, and that is, that as it requires a great amount 
of power to start an elevator from a state of rest, the motor will 
take a very strong current in the act of starting. To get around 
this objection, it is a common practice to provide a separate rope 
for starting the motor, and then when it is desired to use the ele- 
vator, the motor rope is pulled first, and in half a minute or so, 
the main hand rope is pulled. In this way the motor gets a start 
ahead of the elevator, and the headway of the motor armature 
helps to set the elevator car in motion, so that the current taken 
by the motor to start the elevator is very much reduced. 

When a separate rope is used to start the motor in advance of 
the elevator, the starter E, or the levers connecting with it, are 
made so that while the motor can be started independently of the 
elevator car, when the main hand rope is pulled to stop the car, 
it also stops the motor. If this arrangement were not provided, 
the operator might stop the elevator and forget to stop the motor, 
in which case the latter would keep on running and waste power. 

The main hand rope I is provided with stops at top and 
bottom of the elevator shaft, so that the car may be stopped auto- 
matically should the operator forget to pull the hand rope at the 
proper time. 

It is the universal practice with elevator machines of the type 
shown in Fig. 1 to counterbalance the elevator car, but I have 
not shown a counterbalance in this diagram as it would only serve 



722 



HANDBOOK ON ENGINEERING. 



to complicate its appearance, and it is not necessary to show it as 
the electrical features will be the same whether there is a counter- 
balance or not. This diagram also shows a separate rope h for 
actuating the starter E^ but in actual machines E is generally 




^LEIYATOR 



DIAGRAM SHOWING CONNECTIONS 
GRAVITY MOTOR CONTROLLER 
ELEVATOFf 




operated from the lower sheave a, which also actuates the belt 
shifter. 

Fig. 2 is a diagram that shows the way in which one of the 
various motor starters in actual use is connected with the motor 



HANDBOOK ON ENGINEERING. 



723 



and the operating hand rope. In this illustration A is the lower 
sheave a of Fig. 1, and F represents the hoisting drum and E the 
driving pulleys of the elevator machine, G being the lifting ropes 
from which the car is suspended. The sheave A is rotated 



\///////////////////////// ///////////////A 




DIAGRAM or CONNECTIONS OF A 



'-H 



GRAVITY MOTOR CONTROLLER. 
\NITH SEPARATE ROPE ATTACHMENT. 



(^ca O 




through one quarter of a turn in either direction by the pull on 
the hand rope B, and when so rotated shifts the belt shifter and 
also lifts the brake from the brake-wheel. At the same time the 
crank pin C pulls up the connecting rod, and thus the upper end 



724 HANDBOOK ON ENGINEERING. 

of rod c, which takes the place of lever c in Fig. 1. In this 
way the switch blades in the lower end of c are raised into con- 
tact with the clips J*;, which take the place of contact/ in Fig. 1, 
and thus the circuit is closed. A projection s on c holds the 
switch e in the upper position, but when c is raised, s goes up with 
it, and then e is free to descend by the force of gravity acting 
upon the weight iv. The dash pot m is set so as to retard the 
movement of e as much as may be desired. The outer end of e 
glides over the contacts i in its downward movement, and thus 
cuts out of the armature circuit the starting resistance. This 
resistance is contained in the controller box. 

Fig* 3 shows the same type of controller as in Fig. 2, but it is 
arranged so that the motor may be started ahead of the elevator. 
The separate motor-starting rope is shown at H. When this rope 
is pulled, it elongates the spiral spring ^ which is connected with 
the stud G fixed in the upper end of rod c. The rope H is pulled 
up enough to stretch K until the lever Dis lifted, ^ being attached 
to its outer end I. When D is hfted sufficiently, its inner end dis- 
engages the stud G, and allows it to slide upward in the slot 
shown in dotted lines, in the lower end of the connecting rod. 
In this way the motor is started ahead of the elevator machine. 
If now the elevator machine is started, by pulling on the main 
hand rope FF, the crank pin C on the hand rope sheave will lift 
the connecting rod C, and when it reaches its upper position, the 
catch-lever D will drop into the position shown in the illustration, 
and thus lock the stud G, so that when the' elevator is stopped, 
the rotation of the hand rope sheave will push rod C downward 
and thus stop the motor, as well as shift the belts and stop the 
elevator machine. 

In the three illustrations shown the motor is run alwaj^s in the 
same direction and the reversing of the direction of rotation of 
the hoisting drum is effected by the use of double belts and a 
belt shifter, or friction clutclies which cause one or the other of 



HANDBOOK ON ENGINEERING. 725 

the belts to do the driving. The way in which machines of this 




type are installed can be more fully understood from Fig. 4. 



726 HANDBOOK ON ENGINEERING. 

This figure shows the position of the motor, the countershaft 
and the elevator machine with reference to the elevator shaft. 
This illustration is so clear that an explanation of it would be 
superfluous. 

In relation to the installation of elevator plants of this type 
all that need be said is that the motor must be of the shunt 
type, the same as those used for driving machines of any kind. 
A series wound motor, such as are used for electric railway 
cars, must not be used. Shunt wound motors cannot run above a 
certain speed, unless forced to do so by power applied from an 
external source, and in such an event they become generators of 
electricity and thus resist rotation. On this account, when they 
are used for elevator service, they not only move the elevator car, 
but when the latter is descending under the influence of a heavy load 
and tends to run away, the motor at once begins to act as a gen- 
erator, and is thus converted into a brake which holds the car and 
prevents it from attaining a speed much above the normal ; in 
fact, the difference between the car velocity when lifting a heavy 
load, and when running down under the influence of a similar load 
is hardly enough to be noticed by any one not familiar with the 
elevator. 

The motor in these combinations is to be given the same care 
as those used for other purposes ; that is, it must be kept clean 
and the brushes properly set so as to run with as little spark as 
is possible. The controller switch requires more attention than the 
motor starters used with stationary motors, for the simple reason 
that it is used to a much greater extent. Every time the elevator 
is started or stopped the controller switch is actuated, hence, the 
switch levers are subjected to a considerable amount of wear, and 
the contacts are liable to become rough, either by cutting or by 
being burned on account of making imperfect contact. On this 
account the contact must be well examined at least once every 
day, and if burned or rough must be smoothed up. It is also 



HANDBOOK ON ENGINEERING. 



727 



necessary to see that all parts of the controller are properly se- 
cured, that none of the screws or pins are working out, and that 
the contacts and switch levers are not out of their normal posi- 
tion. 




As electric motors can be run as well in one direction as the 
other, and as all that is required to make any motor reversible is 
to provide a reversing switch, it can be seen at once that by mak- 
ing use of such a switch, the direction of movement of the ele- 



728 HANDBOOK ON ENGINEERING. 

vator car can be reversed by simply reversing the motor, and thus 
do away with the complication of a countershaft and tight and 
loose pulleys. Owing to this fact elevator machines are now 
made so as to be used with reversing motors. These are usually 
called single-belt machines. The way in which such machines 
are connected with the motor and the type of controller required 
can be under stoood from the diagram Fig. 5. 

As will be seen, the principal difference in the machine itself 
is that the tight and loose pulleys are replaced by a single tight 
pulley which is only wide enough to carry the driving belt. 
Usually an extra pulley is provided for the brake, and this brake 
is mechanically operated in the same manner as upon machines 
provided with shifting belts. Another modification which is 
sometimes used, but is not shown in the diagram, is the arrange- 
ment of a brake so that same is operated by a magnet 
instead of by mechanical means. With this arrangement the 
magnet is arranged so that when the machine is in motion, the 
current passing through the magnet coil acts to lift the brake, 
and when the machine stops, the magnet lets go, and the brake 
goes on. By arranging the brake in this way it becomes perfectly 
safe ; for if the brake magnet fails to act, the brake will not be 
raised, and the machine will not move ; that is, failure of the 
device to work properly will not permit the elevator car to move, 
thus calling attention to the fact that something is out of order. 

The operation of the reversing controller is as follows : the 
current from the line wires passes along the dotted connections 
h h to the contact ?',i, i,i. The upper left hand i contact is con- 
nected with the lower right hand one, and the upper right hand 
with the lower left hand. The switch lever c is connected with 
lever e by means of the two springs r r, so that c may be moved 
either up or down without carrying e with it. The curved con- 
tact is connected with j and the stud around which c and e 
swing is connected with k, while g is connected with the ends of 



HANDBOOK ON ENGINEERING. 729 

the starting resistance n n by means of the wire / and the two 
wires s s. If the hand rope I is pulled so as to carry lever c 
upward, the current from the left side line wire will pass through 
upper left side i contact, to o, and thence to J and through wire h 
to the motor armature and returning through the other h wire will 
reach g and then pass through /and lower s to lower end of n and 
thence to lever e and the inner end of lever c, which will be rest- 
ing on the upper right side i contact, thus reaching the right side 
line wire. The current for the field magnet coils will be drawn 
from j through wire d and back to k through the other wire d. 
As lever c has been moved upward, the upper spring r will be 
compressed, and the lower one will be stretched, hence a force 
will be exerted to move e downward over the lower contacts n and 
thus cut out the starting resistance. As in the case of the con- 
troller in Fig. 1 the dash pot m by its resistance retards the move- 
ments of e, so as to cut out the resistance as gradually as may be 
desired. 

In the chapter on stationary motors it is shown that to prevent 
destructive sparking, when the starting switch is opened, the 
armature and field coils are connected so as to form a permanently 
closed loop. This style of connection is used in the non-revers- 
ing controller of Fig. 1, but it cannot be employed with a revers- 
ing controller, because both ends of the armature circuit must be 
free, so that they may be reversed when the direction of rotation 
is reversed. As this connection cannot be made, a very common 
expedient resorted to to prevent serious sparking when the switch 
is opened is to connect a string of incandescent lamps across the 
terminals of the field circuit, as is indicated at v -y i;. These 
lamps, together with the field coils, form a closed circuit, so that 
when the switch is opened, the field can discharge through the 
lamps, and thus avoid sparking at the controller contacts. The 
only objection to this arangement is that all the current that 
passes through the lamps is wasted, but by placing two or three 



730 HANDBOOK ON ENGINEP^RING. 

in series the loss is reduced to an insignificant amount. Another 
way in which the sparking is subdued, but only to a slight ex- 
tent, is by connecting the brake magnet coil with the binding 
posts/ and k^ which is the simplest and most generally used con- 
nection. The brake magnet coil together with the field coils form 
a closed loop when connected with J and A;, but when the main cir- 
cuit is opened, the currents flowing in the two coils meet each other 
at J and k flowing in opposite directions, hence they both follow 
along the main circuit and try to jump across the gaps at the 
switch, and thus produce about as much sparking as if they were 
connected independently of each other. In tracing out the path 
of the current when lever c is moved upward, it was shown that the 
left side line went directly to the upper commutator brush. Now 
when c is moved downward, this same line wire runs to the lower 
commutator brush since the connections between the two upper 
i contacts and the two lower ones are crossed. To reverse the 
direction of rotation of a motor all that is required is to reverse 
the direction of the current through the armature, that through 
the field remaining unchanged, hence it will be seen that by cross- 
ing the connections between the upper and lower i contacts, the 
direction of rotation of the motor is reversed when the c lever is 
moved in opposite directions. 

DIRECT CONNECTED ELECTRIC ELEVATORS. 

The machines explained in the foregoing pages are simply 
combinations of an electric motor and a belt driven electric ma- 
chine, but, as already stated, they are commonly spoken of as 
"electric elevators." In what follows it is proposed to explain 
the construction and operation of true electric elevators, which 
are called ' ' direct connected machines ' ' to distinguish them from 
the combinations so far described. 

There are many designs of direct connected electric elevators 



HANDBOOK ON ENGINEERING. 



731 



now upon the market, and it would be out of the question to un- 
dertake to describe all of them in the space that can be devoted 
to the subject in this book. On that account the discussion will 
be confined to the designs that are most extensively used. The 
explanations here given, however, will be sufficient to enable any 




Fisj. 6. 



one to understand the operation of any of the machines not de- 
scribed because the difference in the principle of operation is 
only slight. 



732 HANDBOOK ON ENGINEERING. 

Perlia23s the type of direct connected electric elevator that | 
is most extensively used is the Otis drum elevator with hand 
rope control which is illustrated in Fig. 6. This machine has 
been upon the market for twelve years or more, and is still one of 
the standard Otis machines. It is called a hand rope control 
machine because the starting and stopping is controlled by the 
movement of a hand rope that passes through the elevator car. 
In the illustration, the sheave around which the hand rope passes 
can be seen located on the front end of the drum shaft. In a 
modification of the design, this sheave is mounted upon a sep- 
erate shaft but the way in which it acts is the same as in the pres- 
ent design. When the hand rope is pulled the sheave is 
rotated and the horizontal bar, running from it to the 
controller box, which is mounted on top of the motor i 
shifts the starting switch so as to run the machine in 
the direction desired. At the same time, the vertical lever ex- 
tending upward from the side of the brake wheel, lifts the brake 
and thus frees the motor shaft so that it may revolve unobstructed. 
The motor carries a worm on the end of the armature shaft which 
gears into the under side of a worm wheel mounted upon the 
drum shaft. This worm wheel runs in a casing seen just back of 
the hand rope sheave wheel. The sheave mounted upon the shaft 
directly above the drum is for the purpose of guiding the coun- 
terbalance ropes which run up from the back of the drum. In 
some buildings these rojjes can be run up straight from the back 
of the drum, but in most cases they must run up in the elevator 
shaft in the space between the car and the side of the shaft. As 
these ropes wind upon the drum from one side to the other, the 
guiding sheave must move endwise on the shaft, hence it is called 
a traveling, or vibrating sheave. The levers seen projecting to 
the right of the machine from a small shaft just above the drum 
are what is called a slack cable stop, and their office is to stop 
the machine if the lifting cable becomes slack through the wedg- 



HANDBOOK ON ENGINEERING. 733 

ing of the car in the elevator shaft or any other cause. These 
levers are held in the position shown when the lifting ropes are 
tight, but drop out of position if the rope slackens up, and in 
dropping they release a lever which holds the weight seen under 
the hand rope sheave. The movement of this lever operates a 
catch that engages with the hand rope sheave and thus the hori- 
zontal bar that operates the brake and the controller switch is 
brought to the stop position and the rotation of the hoisting drum 
is stopped. 

The hand rope bas fastened to it at the top and bottom of the 
elevator shaft stops that are moved by the car when it reaches 
either end of its travel, and thus the elevator machine is stopped 
automatically. This arrangement is the same as that used with 
the belt driven machines already described, but as an additional 
safety, a stop motion is provided on the machine itself, so that if 
the stops on the hand rope become displaced, the car will still be 
stopped automatically at the top and bottom landings. This stop 
motion is seen on the end of the shaft, just in front of the hand 
rope sheave, and consists of a nut that travels on the shaft as the 
latter revolves. At both sides of the screw there are projection 
cases upon the inclosing frame, which are struck by the traveling 
nut when it comes near enough to either end. When the nut 
strikes the projection, the hand rope sheave is revolved with the 
shaft and thus the machine is stopped. To understand this ac- 
tion it must be remembered that the hand rope sheave does not 
revolve except when turned by the pull on the hand rope or by 
the action of the slack cable stop or the traveling nut. 

The controller box on top of the motor contains the starting- 
resistance, the starting and reversing switch, and also a magnet 
to. actuate a switch that gradually cuts out the starting resistance. 
The way in which the switches act to start and stop the motor 
can be readily explained by the aid of the diagram Fig. 7. 

This shows the circuit connections in the simplest possible 



734 HANDBOOK ON ENGINEEKING. 

form. In this diagram all the wires whose presence would make 




SAFETY MAGNET FOR 
BRAKE ON MACHINE 



SHUNT FIELD 

the drawing confusing have been removed, but the manner in 



HANDBOOK ON ENGINEERING. 735 

which they are connected will be readily understood from the 
following explanation : — 

The main switch, which connects the motor circuits with the 
line, is located at the upper left hand corner of the diagram, the 
main line wires being marke + and — . When this switch is 
closed, the motor circuits are connected with the line, but the 
motor circuit itself is not closed so long as the switch M remains 
in the position shown. When this switch is turned about one 
quarter of a revolution in either direction, one end will ride over 
the upper contact and the other one over the lower contact. 
The reversing drum and switch M are mounted on the same 
spindle and move together. They are located within the con- 
troller box, on top of the motor, and are moved by the horizontal 
bar ; see Fig. 6. The shaded portions of the drum, on which the 
brushes h and i rest are made of insulating material so that when 
switch M and the reversing drum are in the position shown the 
motor circuit is open at two points. This is the position of these 
parts when the machine is stopped. 

The starting; resistance is shown above the reversing drum, 
and in the machine it occupies the space at the back of the con- 
troller box, shown on top of the motor in Fig. 6. The segment 
i? is a series of contacts that are connected with the resist- 
ance in the resistance box; No. 2 contact being con- 
nected with point 2 on the resistance and so on for all the other 
numbers. The switch arm JV^is moved over the contacts i2 by a 
magnet that is represented by the spiral L. The motor arma- 
ture and the shunt and series field coils are shown at the bottom 
of the diagram. The motor is compound wound, it being made 
so for the purpose of keeping the starting current as low as possi- 
ble. The path of the current through the wires is as follows : Sup- 
pose the reversing drum andtheJf switch are revolved in the direc- 
tion in which the hands of a clock move, then brushes^ and i will 
rest on one segment, and h and k will rest on the other segment. 



736 HANDBOOK ON ENGINEERING. 

As switch ilf" will now be closed, the current will flow to brush 
g and through the reversing drum segment to brush i; then it 
will follow the wire to the right side I of the armature and pass- 
ing through the latter will reach wire E and thus brush /i, from 
which it will pass to brush k. From this brush the current will 
go to and through magnet L and by wire C ' and switch N will 
reach contact No. 10. As this contact is connected with point 
10 of the resistance the current will reach the latter and will pass 
through the whole of it, coming out at the opposite end Q. This 
end is connected with contact C, so that from this segment the 
current can flow through wire Q to the end F of the series field 
coils, and passing through these to end H^ will find its way to 
wire /, and thus return to the opposite side of the main line. 
From this explanation it will be seen that the current will pass 
through the motor armature, and then through the whole of the 
resistance in the resistance box, and then through the series field 
coils, and finally reach the other side of the main line. From 
the switch M another current will branch off and run to binding 
post i), and thence through the shunt field coil to binding post 
A" and thus to wire/, and through the latter to the opposite of 
the main line. 

The switch lever ^ is in some cases arranged so that the mag- 
net L acts to hold it upon contact 10 and a spring acts to carry 
it forward toward contact A; in other cases the magnet is wound 
with two coils, one of which pulls N in one direction and the 
other pulls it in the opposite direction, the two coils being so j)ro- 
portioned that iV moves gradually from contact 10 toward con- 
tact A. If we take the spring arrangement, then magnet L will 
pull N back toward contact 10, and the spring will pull it forward. 
As the starting current is very strong, A^will be held on contact 
10, but as the current weakens, the spring will begin to overpower 
the magnet, and N will slide over contact 9 and then 8 and 7 and 
so on to contact A. As contact 9 is connected with the point 9 



HANDBOOK ON ENGINEERING. 737 

of the resistance, when breaches it, the section of the resistance 
between points 10 and 9 will be cut out. When JS^ reaches con- 
tact 7 the resistance between points 10 and 7 will be cut out for 
the latter point is connected with contact 7. As all tlie contacts 
are connected with the corresponding points of the resistance, 
when iV reaches contact C, all the resistance in the resistance box 
will be cat out of the circuit. As will be noticed, contact B is 
connected with the center point G of the series field coil so that 
when N reaches contact B one-half of the series coils will be cut 
out in addition to the whole of the resistance box. When N 
reaches contact ^1 the current will pass directly to wire/, and thus 
cut out all the series field coils and then the motor will run as a 
plain shunt- wound machine, and its speed will be the highest it 
can attain. 

If the reversing drum and switch M are now revolved to the 
position shown in the diagram, the circuit through the motor will 
be broken and the machine will come to a state of rest. If the 
reversing drum and If are now revolved in the opposite direction, 
that is, contrary to the movement of the hands of a clock, the 
brushes g and h will rest on one of the revolving drum segments, 
and i and k on the other segment. If the path of the current is 
now traced it will be found that it will enter the armature through 
wire jE", and the left side, instead of through wire /, as in the pre- 
vious case. It will also be found, however, that the current after 
passing through the armature will reach the series field coils 
through F, which is the same path as before, so that the direction 
of the current has been reversed through the armature only, 
which is what is required to reverse the direction of rotation of 
the motor. Whichever way the switch Jf and the reversing drum 
are turned, the direction of the currents through the series field 
coils and the shunt field coil will be the same, and only the arma- 
ture current will be reversed. 

Cutting out the series field coils not only increases the speed 

47 



738 HANDBOOK ON ENGINEERING. 

of the motor, but obviates the danger of the car attaining a dan- 
gerously high speed if the load is being lowered. A shunt wound 
motor will run as a motor up to a certain speed, but if the veloc- 
ity is forced above this point by driving the machine by the ap- 
plication of external power, then the motor will begin to act as a 
generator, and as it takes power to run a generator the motor will 
begin to hold back. Now if an elevator car is running down 
with a heavy load, the load will draw the car down, and unless a 
resistance of some kind is interposed, the speed will become 
greater and greater as the car descends, and by the time it 
reaches the bottom of the shaft it may be running at a velocity 
almost equal to that attained by a free fall. The power required 
to drive the motor when acting as a generator serves to hold the 
car back, for the current developed increases very rapidly with 
increase of speed, so that an increase of speed of ten or fifteen 
per cent above the normal running velocity will be about as much 
as can be reached even with an extra heavy load. 

Although the motor will act as a generator and hold the car so 
that it cannot attain a dangerous speed when descending under 
the influence of a heavy load, it will only accomplish this result 
when the circuit is closed ; for if the circuit is open there will be 
no power generated ; hence, no power will be absorbed by the 
motor. As can be readily seen, it is possible for the circuit out- 
side of the motor to become broken by the melting of a fuse or 
some other cause, and if this occurs when the car is coming down 
with a heavy load there might be a serious accident. To obviate 
such mishaps the main switch is made with a magnet b which 
holds the switch closed so long as current passes through it, but 
allows the switch to swing open if the line current disappears. 
This switch on this account is called a potential switch, because 
it is arranged to be actuated by the difference of potential be- 
tween the two sides of the line. When the line current fails, and 
the potential switch opens, the blade m comes into contact with n 



HANDBOOK ON ENGINEERING. 739 

and thus the circuit for the motor armature is closed through the 
resistance wire s which is connected with contact 7. This con- 
nection short circuits the armature through a resistance sufficient 
to keep it from being burned out, but not enough to prevent the 
motor from acting as a brake and holding the car down to a safe 
speed. 

The wire c c which runs from magnet b of the potental switch, 
it will be noticed, connects with a coil marked safety brake mag- 
net. This magnet acts normally to hold the brake off when the 
machine is running, but if the current passing through it dies out, 
then it acts to put the brake on. Now, as has already been ex- 
plained, when the current is flowing in the main line, there is a 
current passing through coil 6 of the potential switch ; hence, 
there is a current passing through the coil of the safety magnet for 
the brake ; but if the line current fails the current through the 
brake magnet will also fail and the brake will go on ; so that the 
car will be doubly protected, one protection being the short cir- 
cuiting of the motor circuit through wire s, and the other the ap- 
plying of the brake by reason of the failure of the current to flow 
through the safety brake magnet. 

As to directions for the proper care of these machines, very 
little need be said, as they are simple and substantial in con- 
struction and give very little trouble. The motor proper requires 
the same attention as is given to any stationary motor, that is, 
the commutator and all other parts must be kept as clean as pos- 
sible and the brushes must be properly set. As to the other 
parts, all that need be said is that the bearings must be well lubri- 
cated and free from grit. They must be tight enough to not al- 
low the parts to play, but at the same time care must be taken 
that they are not so tight as to heat up or cut. All bolts and 
nuts must be regularly examined and kept tight, so that they 
may not work loose or out of place. The most important point 
to observe, however, is not to undertake under any circumstances 



740 HANDBOOK OJ^ ENGINEERING, 

to tinker with the sheave wheel and the gears that connect it with 
the horizontal bar that operates the brake and controller 
switches. Neither must the brake or the switches be disturbed. 
All that is to be done to the latter is to keep the contacts bright 
and clean. If any of these parts, from the sheave wheel to the 
controller switches, get out of set, so that the machine will not 
run satisfactorily, do not undertake to readjust them, but send 
for an expert from the elevator company. If any of these parts 
are removed or shifted there is danger of their not being put 
back in their proper position, and if they are misplaced a very 
serious accident may be the result. If the proper adjustment of 
these parts is destroyed, the elevator will not stop automatically 
at the top and bottom landings, but will run too far at one end 
and stop short of the mark at the other ; hence, the car may 
either strike violently against the floor or run at full speed into 
the overhead beams, and in either case the results might be very 
serious. Even elevator experts have to go cautiously in adjust- 
ing the position of the sheave wheel and the parts connected 
with it. 

The fact that those not thoroughly posted in the operation of 
these elevators should not tamper with the hand rope sheave and 
its connections, is not at all unfortunate, for it is next to impos- 
sible for them to get out of place ; but special caution is advised 
at this point, because there are many men who are apt to take it 
for granted that if the machine runs poorly from some trifling 
cause that they have not been able to locate, the trouble must be 
due to some defect in the adjustment of the several parts of the 
operating sheave and its connections. They will then proceed to 
pull the machine apart, and when they put it together again they 
are very liable to get it connected wrong, and if such should be 
the case the first trip made by the elevator might end seriously. 

Although the machine described in the foregoing works in an 
entirely satisfactory manner, it has been superseded almost en- 



HANDBOOK ON ENGINEERING. 



741 



tirely in first-class iiistallatioiis of recent date by machines iliat 
are controlled by means of a small switch in the car instead of 
the hand rope. There are several types of such elevators made 
by the Otis Company, one of the latest designs being shown in 
Fig. 8. 




Fig. 8. 

As will be noticed at once, this machine is different in several 
respects from" the hand rope control machine shown in Fig. 6. As 
the machine is controlled by the movement of a switch in the car, 
the brake cannot very well be actuated mechanically, hence a 
magnetic brake is provided, the magnet being seen at the top of 
the stand to the right of the motor. The automatic stopping de- 
vices and the slack cable stop are also arranged so as to act upon 



742 



HANDBOCK ON J3NGINEERING. 



switches, which are contaiaed within the casings seen at the front 
end of the hoisting drum. The controller for this type of 
machine is not placed on top of the motor, generally, for since it 



COA/TROLlE/f 




c^9 

is not connected mechanically with any of the moving parts of the 
machine, it can be located at any convenient point, and is then 
connected with the motor armature, field coils and with the brake 



HANDBOOK ON BpfGINEERING. 743 

magnet and automatic stop switches by means of copper wires. 
The controller used with this type of machine is arranged after 
the fashion of a switchboard, the switches being located on the 
front, and the connecting wires, together with the starting resist- 
ance, being at the back. The switches are actuated by means of 
electromagnets, and on that account the device is called a magnet 
Controller. The diagram of the wiring connections with this con- 
troller is more complicated than that for the hand rope controller, 
but for the purpose of simplifying the drawing as much as pos- 
sible I have removed all the connections that are not actually 
necessary for a proper understanding of the general arrangement 
of the circuits. This simplified diagram is shown in Fig. 9. 

The front of the controller is shown in Fig. 10, and the back 
of same in Fig. 11, the starting resistance being removed in this 
illustration so as to afford a clear view of the wire connections. 
The side of the starting resistance can be seen in Fig. 10. In 
this last named illustration, all the switches are in the position 
they take when the elevator is stopped. The two large switches' 
on either side at the bottom of the board are the starting switches, 
one acting to run th€ car up and the other one to run it down. 
The two smaller switches occupying the center of the bottom 
panel of the board and the two switches in the upper corner are 
for the purpose of accelerating the velocity of the motor when it 
is started. When the motor starts, there is a resistance in the 
armature circuit, and the current after passing through the arma- 
ture is passed through series field coils. After the motor has 
started, the starting resistance is cut out, and then the series field 
coils are cut out, so that when the full speed is attained, the 
motor is a simple shunt-wound machine. In this respect the 
arrangement of the motor circuits is the same as in the hand rope 
controller machine. 

When it is desired to start the car, a small switch in the latter 
is moved toward the right or left, according to the direction in 



744 



HANDBOOK ON ENGINEERING. 



which the car is to move. To run the car uj), the car switch is 
turned to the left, and this movement sends a current through the 
magnet of the lower right side magnet on the controller board. 



^*ir^ 




Fig. iO. 

This magnet then lifts its plunger and the two discs mounted upon 
the latter come into contact with the stationary connectors located 
just above them, and then the current can find its way through 



HANDBOOK ON ENGINEEKINGo 



745 



the motor circuits iu the proper direction to produce the upward 
motion. The four small switch magnets on the controller board 
are connected in separate circuits that are in parallel with each 





Fig. 11. 

other, and in shunt relation to the armature of the motor. When 
the motor first starts, the counter electromotive force developed 
by the armature is not as great as when it is running at full speed. 



746 HANDBOOK ON ENGINEERING. 

because a portion of the electromotive force of the line current is 
used to force the current through the starting resistance and 
through the series field coils. When a portion of the starting 
resistance is cut out the armature counter electromotive force is 
correspondingly increased. When more of the starting resistance 
is cut out, the counter electromotive force is further increased. 

It is still further increased when the series field coils are cut 
out. Now the current that passes through the magnets of the 
four small switches on the controller board increases as the counter 
electromotive force of the motor armature increases. The mag- 
nets are so adjusted that as the currents passing through them 
increase one after the other will lift its plunger and then the con- 
nections made by the discs at the lower end of these plungers will 
cut out successively the sections of the starting resistance and the 
sections of the series field coils. The two small tubes at the top 
of the controller board are safety fuses, and the line wires are 
connected with their ujDper ends. 

By the aid of the foregoing explanation of the way in which 
the controller acts, the following description of the wiring diagram 
(Fig. 9) will be easily understood. In this diagram the line 
wires come in at the top of the controller and are marked + and 
— . The motor is shown at the bottom of the diagram, the circle 
A representing the armature, and the coil B is the brake magnet. 
The stop motion switch is placed on the elevator machine, in one 
of the casings at the front end of the drum, and is actuated by 
the automatic stop mechanism which stops the car at the top and 
bottom landings. The car switch is shown in the upper left hand 
corner of the diagram, and the curved lines J represent the wires 
that connect it with the motor and the controller board. These 
wires are placed within a flexible cable that is attached to the 
side of the elevator shaft half the way up from the bottom, the 
cable being long enough to reach the car when at either end of 
the shaft. The limit switch in the car is for the jDurpose of stop- 



HANDBOOK ON ENGINEERING. 747 

ping the motor, if the car reaches either end of its travel without 
being stopped by the operator, or the action of the stop motion 
switch. This switch is closed under ordinary conditions, so that 
the current in wire C can flow all the way to the lower contact a 
of the car switch. If it is desired to run the car down, the car 
switch is turned to the right, and then wire C is connected with 
wires D ' and FD. The stop motion switch is normally in the 
position shown so that the current in wire D ' can pass to Dq and 
following this wire it will reach contact Dq which is under the 
lower disc of the right side starting switch. Through the disc 
this contact is connected with the corresponding contact on the 
other side of the disc, and this latter contact is connected with a 
wire that carries the current to the magnet of the left side starting 
switch. Considering now the main current in the + line it can 
be seen that it can flow down to the line near the bottom of the 
controller portion of the diagram, and which terminated in the 
-\- contacts of both the starting switches, but can go no further 
so long as the discs on the plungers of the magnets are in the 
lower position. As soon, however, as the current coming frpm 
the car switch passes through the magnet of the left side switch, 
as just explained, the plunger will be lifted, and then the disc will 
connect the + contact with the /iS2 contact, and also with a 
smaller contact B. When this connection is made, the main cur- 
rent can flow from contact S2 to contact /S2 of the right side 
switch, and thence through the connecting disc to contact I which 
is connected by wire to binding post I; the latter being con- 
nected with the right side armature terminal /. After passing 
through the armature the main current reaches binding post E 
and through the connecting wire the contact E at the top of the 
left side starting switch, and as the plunger of this switch is in 
the raised position, the current can pass to contact R and thus 
reach the upper end B, of the starting resistance in the resistance 
box. 



748 HANDBOOK ON ENGINEERING. 

From the end F of the starting resistance, the main current 
flows to binding post F and then to the F end of the series field 
coils, and from end H to binding j^ost // and to the — line wire 
at the top of the diagram. The current for the shunt field is 
taken from the contact S2 at the bottom of the left-ride starting 
switch, and passes to point iS4 and thence to D and to the D end 
of the shunt field coil, and through this coil to end H of the series 
coil, and thus to the — line. The current for the brake magnet 
starts from the small contact B at the bottom of the left-side 
starting switch. 

The car switch when moved will first cover contact D' so that 
the main current will follow the path outlined above, but as 
soon as the car switch covers contact FD^ the current passing- 
through wire FD in the cable will reach the stop-motion switch 
and pass to F, and thus to magnet No. 1 at the upper lef b hand 
corner of the controller board. The lifting of this switch will 
cause its disc to connect the contacts RE' and thus the current 
will pass to point W of the resistance and cut out the upper sec- 
tion. The current from contact B at the bottom of the left-side 
starting switch passes through the magnet coils of the three 
switches, Nos. 2, 3 and 4. Now soon after the first section of 
the starting resistance is cut out. No. 2 magnet becomes strong 
enough to lift its j^lunger, and then the current from the right 
side, contact i^, at the top of the left-side switch, will pass to 
contact R of No. 2 switch, and thus to R2 and to point R2 of 
the resistance, thereby cutting out two sections. In this way the 
current through magnet of switch No. 3 will be increased and the 
plunger will be lifted so that the current will be able to pass from 
the R contact of this switch to the G contact, and thus to binding 
post G and to the center of the series field coils, thereby cutting 
out one-half of these coils. In this way the current through coil 
of No. 4 magnet will be farther increased, so that it will be able 
to lift its plunger, and thus form a direct connection from contact 
G of switch No. 3 and the main wire leading to the — line. 



HANDBOOK ON ENGINEERING. 749 

Thus it will be seen that the four switches, 1,2, 3 and 4, will 
act one after the other. This same operation is repeated if the 
car switch is moved to the right, so as to run the elevator down, 
the only difference being that the starting switch at the right side 
of the board will be lifted, but the action of the four smaller 
switches will be the same. 

In addition to the operating circuits described in the foregoing- 
there are wires that connect the slack cable switch with the motor 
circuits and other connections by means of which the elevator may 
be run from the controller board whenever desired. These con- 
nections are not shown in Fig. 9, as they would complicate the 
drawing, and it is not thought advisable to complicate the explan- 
ation of the main part of the system for the sake of introducing 
the minor details. 

This type of electric control is used for elevator building in- 
stalled in office buildings, and others placed where the car is oper- 
ated by a regular attendant. For private house elevators and for 
dumb waiters it is necessary to modify the controlling system so 
that the car may be operated not only from within, but also from 
any of the floors of the building. It is further necessary that 
the circuit connections be such that if the car is operated from 
any floor, it will run to that floor, whether above or below it, and 
further, so that if it is being operated by a person within the car 
it cannot be operated by any one else from any of the landings. 
It must also be arranged so that if the car is set in motion from 
any floor it cannot be stopped or interfered with in any way by 
a person at another floor. For the purpose of safety the system 
must also be arranged so that the car cannot move away from any 
floor until the landing door is closed. This feature is necessary 
to guard against people falling through the open doorway into the 
elevator shaft. Although it would appear difficult to accomplish 
all these results without resorting to great complications, as a 
matter of fact the system used by the Otis Company is decidedly 



760 



HANDBOOK ON ENGINEERING. 




OOOH CONTACTS 



HANDBOOK ON ENGINEERING. 751 

simple. At each floor of the building a push button is placed, 
and by pressing this for an instant the car is set in motion wher- 
ever it may be, providing it is not being used by some other per- 
son, and when it reaches the floor from which it has been operated 
it will stop automatically. If the elevator is operated from the 
car, a button is pushed that corresponds to the floor at which it 
is desired to stop, the car will then begin to move, and when the 
floor is reached it will stop. If the passenger after stepping out 
of the car forgets to close the landing door, the elevator cannot 
be moved away from the landing by the manipulation of any of 
the push buttons on the various floors or within the car. The 
way in which all these results are accomplished can be made 
clear by the aid of Fig= 12, which is a simplified diagram of the 
wiring. 

In this diagram most of the parts are marked with their full 
name. The floor controller is a drum which is revolved by the 
elevator machine and its office is to shift the connections of the 
wires 11, 22, 33, 44, from one side of the circuit DU to the 
other as the car ascends and descends in the elevator shaft. This 
shifting of these connections is necessary to cause the car to run 
down if above the landing from which it is operated, and to run 
up if it is below the landing. The actual position of the floor con- 
troller with reference to the elevator machine can be seen in Fig. 
13 in which the floor controller is located back of the motor and is 
driven from the drum shaft by means of a chain and sprocket wheel. 
In the diagram Fig. 12 it will be noticed that the drum surface is 
divided into two segments and upon one rests the brush of wire 
D while upon the other rests the brush of wire Z7. The twelve 
contacts shown at G form the operating switch. The center row 
marked m n o p are movable, and the four contacts above them 
as well as the four below are stationary. The center row of con- 
tacts m n p are moved upward by a magnet represented by the 
ijoil D and they are moved downward by another magnet repre- 



752 HANDBOOK ON ENGINEERING. 

sented by the coil U. From this it will be seen that if a current 
comes from the floor controller through wire D the movable con- 
tacts of G will be lifted and will connect with the top row, while 
if the current comes from the floor controller through wire C, the 
movable contacts will be depressed and will make connections with 
the lower row of contacts. 

The main switch that connects the motor circuits with the 
main line is shown at S. As will be noticed, a wire marked d -{• H 
runs from the -f wire to the right side of the diagram, where the 
landing and the car push buttons and their connections are shown. 
This wire runs from top to bottom of the elevator shaft and is con- 
nected with switches that are closed when the landing doors are 
closed, and open when the doors are open. These switches are 
indicated by the four circles marked door contacts, the diagram 
being for a building four stories high. If the door contacts are 
closed, the current can pass as far as the wire marked + which 
runs through the flexible cable to the car. In the car there is a 
switch in this wire and further on a gate contact, which is closed 
when the car door is closed. If these switches are closed, the 
current can return from the car through wire A and run as far as 
the center of the diagram under the main switch S. The floor 
controller is shown in the position corresponding to the car at the 
bottom of the shaft. Suppose now that the landing push button 
I is pressed for a second, then the wires B and I will be connected, 
and the current in wire A will pass to wire B and through the 
push button to wire I and thence to wire tl. The coil between 
wire I and wire II is a magnet, and as soon as the current passes 
through it, it draws the contact to the right and thus provides a 
path for the current direct from wire A to wire 11^ so that the push 
button may be raised without opening the circuit. The current 
in wire II will pass through the floor controller to wire C/and thus 
through magnet U of the operating switch G. This magnet will 
then draw down the moval^le contacts m. n o j), and the main line 



HANDBOOK ON ENGINEERING. 



753 



current from the -j- wire will pass from contact m to wire tn and 
through wire m' to point ?r, hence through wire ?r' to the acceler- 
ating, or starting resistance, and to wire F which leads to tha 
series field coils. Returning from these coils through wire H to 
magnet switch 2 and thence wire n' to contact n, and as this con- 




Fig. 14. 

tact is pressing against the one directly below it, the current will 
flow through the connection to wire E and thus to the armature ; 
returning from the latter through wire I and wire o' to the contact 
below and thus to o and through the permanent connection to 
contact |) and to the lower right hand contact which is connected 



754 HANDBOOK ON ENGINEERING. 

with wire r which runs to the — side of the main switch. The 
shunt field current is derived from wire m' and returns to contact j 
p and thus to wire r through wirep', as can be clearly traced, i 
The brake magnet current starts from the left side contact of G 
through wire -j- B and returns directly to the lower end of | 
wire r. i 

The magnet switches 1 and 2 act in the same manner as those 
in diagram Fig. 9, that is, by the increase in the counter electro- 
motive force of the armature which causes the current that passes 
through them to increase in strength. When magnet I closes its 
switch, the current passes from wire vf to wire F and thus the 
accelerating resistance is cut out. When magnet 2 closes its 
switch the current passes from wire m" directly to w' and thus to 
the armature without going through the series field coils ; thus 
the latter are cut out. 

Returning now to the operation of the floor controller it will be 
seen that as the current is flowing through wire II the circuit will 
be broken if the controller is rotated until the gap at the top 
comes under the brush of wire II. Now the floor controller 
drum begins to turn as soon as the elevator machine moves, and 
it is so geared to the elevator drum that when the car comes op- 
posite the first floor the brush of wire II will be over the upper 
gap, and then the circuit will be open and the magnet U will be 
de-energized and allow switch 6r to move back to the stop position. 

If button No. 4 is pressed instead of No. 1 the car will not 
stop until the gap at the top of the floor controller drum comes 
under the brush wire 44, for the circuit between this wire and 
wire CT" will be closed until that position is reached. 

If the cai* is run up to the fourth floor, as the gap at the top 
of the floor controller drum will then be under the brush of wire 
44, the brushes of wire 11, 22 and 33 will rest upon the same 
segment as the brush of wire D ; therefore, if with the car at 
the top floor a button is pressed at any one of the lower floors 



HANDBOOK ON ENGINEERING. 755 

j;he current will pass from its corresponding wire to wire D and 
.bus through magnet coil D and to wire r' and wire r. The cur- 
ent passing through magnet D will draw the movable contacts of 
the operating switch 6 upward, and thus set the elevator machine 
in motion in the opposite direction from that in which it runs 
When the t/^ magnet is energized. 

In tracing out the circuits from the floor push buttons as just 
pxplained it will be noticed that if any one of them is depressed, 
the current in wire A will flow through wire B to the button de- 
pressed, and then enter the wire returning from that button. 
When the car buttons are depressed the current in wire A will 
pass to wire C and then through the button in the car to the 
Iproper return wire ; that is, to one or the other of the wires 
|l, 2, 3, 4. After entering one of these four wires the current 
follows the same path as it does when one of the floor buttons 
depressed. The magnet B' in the B wire, and the 
magnet (7' in the C wire, are for the purpose of preventing in- 
terference between a person operating the elevator from within 
the car and another one at one of the landings. The B' switch is 
actuated by a magnet thaf is wound with two coils that act in 
ppposition to each other. These coils are shown to the left of B' . 
When the elevator is operated from one of the floor push buttons 
the current in wire A passes through both the coils on the magnet 
of switch B' and as one coil counteracts the other the switch 
is left closed and the current passes directly to wire B. If the 
elevator is operated from within the car the current from wire A 
in passing to wire C passes through one of the coils of the mag- 
net that actuates switch JS', hence this switch is opened and the 
connection with wire B is broken, so that if now any one of the 
floor buttons is pressed it will have no effect as the circuit is 
opened at switch B' . The current flowing through wire C passes 
through a magnet that acts to close the switch C and thus allow 
a portion of the current to pass directly to wire r. This current 



756 HANDBOOK ON ENGINEERING. 

will continue to flow even after the car has stopped at the landing, 
providing the door is not opened. As soon as the door in the 
car, or the landing door, is opened the circuit is broken either in 
wire //or in wire A, and then the car cannot be moved until the 
doors are closed. If it were not for switch C" it would be possi- 
ble for a person at one end of the landings to move the car if he 
pressed the button during the short interval of time between the 
stopping of the car and the opening of the landing door. The 
opening of the door would stop the car, but by this time it might 
be a foot or two away from the floor level. The current that 
passes from switch C to wire r is kept down to a small amount 
by passing it through a high resistance which in the diagram is 
marked 700 w. 

The electrical portion of the Otis electric elevators has been 
supplied for many years to four or five of the leading companies, 
which were controlled by the Otis, and during the last two or 
three years it has been supplied to practically all the prom- 
inent makers, as these are now part and parcel of this 
company ; hence the descriptions given in the foregoing 
are more than likely to cover any case met with in 
practice, for although there are numerous small manufacturers, 
the sum total of their elevators in use is comparatively small. 
The only electric elevators in addition to those described in the 
foregoing that have come into extensive use are those made by the 
Sprague Electric Co. 

These maehines are of two different types, one being the ordi- 
nary drum design, and the other the screw machine. The drum 
machine is similar in its main features to the same type of ma- 
chine of other makers, and it is only in the minor details of con- 
struction that any radical difference can be noted. In the means 
employed for controlling the motion of the motor, however, there 
is a decided difference. In all the Sprague elevators the car is 
controlled electrically, hand rope control not being used in any! 



HANDBOOK ON ENGINEERING. 



757 







758 HANDBOOK ON ENGINEERING. 

case. The drum machines are arranged like those of other makes, 
so that the motor is connected with the main line whether the car 
is going up or down, and acts as a motor or as a generator ac- 
cording to the conditions of the load ; that is if the load is lifted, 
the machine acts as a motor, and if the load is lowered, the ma- 
chine acts as a generator and holds the car back. With the screw 
type of machine, the arrangement is different, the motor acting 
as such in raising the load, but on the descent the motor is dis- 
connected with the main line and acts as a generator, developing 
a current that circulates in a circuit formed by the motor connect- 
ing the wires, and which is entirely independent of the main 
line. In the drum machine, when the motor acts as a generator 
in lowering a load, the current it generates is sent back into the 
main circuit, and at all times the machine is connected with the 
main line, while with the screw type the motor is only connected 
with the mainline when the load is lifted. 

The general appearance of the screw type of Sprague elevator 
is shown in Fig. 14. This illustration represents two machines, 
one placed on top of the other. In buildings where there is an 
abundance of floor space, the machines are all set directly upon 
the floor, but where floor space is limited, they are stacked two, 
three and even four high. 

As can be clearly seen in Fig. 14, a long screw is coupled to 
the end of the motor armature shaft. This screw threads through 
a nut that is mounted in a cross head that carries a number of 
sheaves around which the lifting ropes pass. At the extreme end 
of the machine other sheaves are mounted, these being held in 
stationary supports. The sheaves carried by the cross head 
travel from one end of the machine to the other as the screw is 
rotated. When they are drawn away from the stationary sheaves 
the elevator car is raised, and when they move toward the sta- 
tionary sheaves the elevator is lowered. In this respect the 
action is just the same as in a horizontal cylinder hydraulic ele- 
vator, i 



HANDBOOK ON ENGINEEKINC4, 



759 




Fio'. 15, 



760 HAND BOOK ON ENGINEERING. A 

The iiLit carried by the traveling cross head is so arranged that 
when the latter reaches the end of its travels at either end of the 
screw, the nut is released and then rotates with the screw with- 
out moving the cross head. This forms a perfect top and bottom 
limit stojj, for even if the motor continues to run, the car cannot 
be carried beyond the positions corresponding to the points at 
which the nut slips around in the cross head. 

The brake for holding the machine is mounted upon the outer 
end of the armature shaft, and can be seen at Fig. 14 at the ex- 
treme right hand side. This brake is actuated by a magnet that 
releases it, and a spring that throws it on. When the current is 
on, the brake is lifted and when the current is off the brake goes 
on. In this respect, the action is the same as in all other electric 
elevators. 

The operation of the motor is controlled by a small switch in 
the car, which is connected with the motor circuits by means of 
wires contained in a flexible cable, just like the Otis electrically 
controlled machines. The controller consists of a main switch? 
which is moved by a small motor called a pilot motor, and a num. 
ber of smaller magnetic switches whose action will be presently 
explained. All these parts are mounted upon a switchboard, and 
present the appearance shown in Fig. 15. The pilot motor and 
main switch are located at the top of the board, and the magnet 
switches cover the space below, while the starting and regulating 
resistance is mounted on the back of the board. 

• The complete wiring diagrams for these machines is decidedly 
complicated owing to the fact that there are numerous switches 
and devices whose office is to afford additional safety, or to ren- 
der the control more perfect. When all the parts that are not 
actually necessary to illustrate the system are removed, however, 
the diagram becomes quite simple and can be readily understood. 
ISuch a diagram is shown in Fig. 16. This diagram shows the 
motor together with the screw and sheaves, the elevator car, the 



HANDBOOK ON ENGINEERING, 761 

counterbalance, and the operating switches. The wires marked -|- 
and — are connected with the main line. The switch in the car 
is connected with the controller by means of four wires, marked 
ch d and s. The lower one of these wires, marked s, is connected 
with the stud around which the car switch swings. When the 
car switch is moved onto the upper contact, it connects wire s 
with wire c and then the car runs up. When the car switch is 
moved down onto the lower contact, wire s is connected with wire 
d, and then the car runs down. When the car switch is placed in 
the central position wire s is connected with wire h and then the 
elevator stops. The two switches marked " up limit," "down 
limit," are for stopping the car automatically at the top and bot- 
tom landings. Normally the up limit switch is closed and the 
down limit switch is open. With these switches in this position, 
which is the position in which they are shown in the diagram, the 
current from the -\- wire can pass through the up limit switch to 
wire fc, and thence through wire I to the armature of the motor, 
and then through the field coils, and reach wire m. It cannot go 
beyond this point until the switch C is moved. This is the main 
operating switch, which in Fig. 15 is seen at the top of the board, 
the contacts being arranged in two circles. The pilot motor that 
rotates the arm of this switch, which is clearly shown in Fig. 15, is 
represented in this diagram. Fig. 16 ^ at A. As will be seen in 
this diagram, this motor has a field provided with two magnetizing 
coils, one for the up motion, and one for the down motion, and in 
addition it is provided with a brake to stop it quickly and hold it 
when not in use. The portion of the diagram marked B is the 
reversing switch. 

Let us suppose now that the car switch is moved upward, so as 
to cause the elevator to ascend, then wire s will be connected with 
wire c. From the -j- wire a current will pass through wire a to s 
and thus to c, and through magnet e of switch ^, thus closing this 
switch so as to connect wires h and i. The current in wire c will 



ibZ , HANDBOOK OX ENGINEERING. 

pass to B tiiid through the connecting phite n will reach the end 
of the up field coil of the pilot motor, and then pass through the 
armature of this motor, and finally through the magnet that re- 
leases the brake. The pilot motor will now rotate the reversing 
switch B so that the contact plates will move toward the left. 
This movement will bring plate w under the ends of wires s and ?', 
thus permitting a current from s to pass to i, and as switch g is 



BRAKE RtLEAZE 




OPERATIVE CIRCUITS 



^PRAGUE PRATT SCREW ELEVATOR 



^t^ ^^• 



closed this current will reach wire li and thus the magnet J, 
thereby lifting the plunger switch that closes the gap between 
wire g and the — wire. As the arm of the main switch C 
moves with the reversing switch B^ this arm will ride over the 
contacts on the right side, marked " i[/res." and thus the current 
from wire m will be able to reach wire g after passing through the 
up resistance. 



HANDBOOK ON ENGINEERING. 763 

If the car switch is left on tlie upper contact, the pilot motor 
will continue to rotate until the arm of switch C reaches the top 
of the resistance contacts, marked Full up. When this point is 
reached, the contact plate u of the reversing switch B will pass 
from under wire c and the terminal of the up field of the pilot 
motor, and then this motor will stop rotating. 

If the car switch is not kept on the upper contact very long, 
the pilot motor can be stopped with the arm of switch G at some 
intermediate point on the resistance contacts, thus by the time 
during which the car switch is kept upon the upper contact, the 
amount of resistance cut out of the motor circuit can be con- 
trolled and thereby the speed of the car can be controlled. 

In this operation it will be noticed that the motor is connected 
with the main line and that the current enters through the -j- wire 
and passes out through the — wire. If now we turn the car 
switch downward, the s wire will be connected with the d wire and 
by following the latter to the reversing switch B it will be seen 
that through connecting plate v it is connected with wire z which 
leads to the end of the down field of the pilot motor, thus setting 
the latter in motion in the opposite direction so as to shift the 
contact plates of B toward the right, and at the same time rotate 
the arm of the main switch C to the left, thereby making contact 
with the contacts of the down resistance. With the arm of C in 
this position, it will be seen that the current in wire I can flow 
through the motor armature and field and through wire m to the 
arm of switch C and through the down resistance to wire n and 
thus back to wire ?, thereby forming a closed circuit within the 
motor wires and connections, and disconnected from the main line 
except on the side of the -|- wire. The rotation of B causes the 
connecting plate x to ride upon the terminals of wires s and f , and 
thus a current is sent through the brake magnet so as to lift the 
brake, and allow the elevator machine to run. When the pilot 
motor moves the arm of G so far as to reach the top of the down 



764 HANDBOOK ON ENGINEERING. 

resistance, the contact plate v of the reversing switch B will pass 
beyond the terminals of wires d and z^ thus breaking the circuit 
of the pilot motor and bringing the latter to a stop. 

When the reversing switch B is in the stop position, as shown 
in the diagram, the terminal of wire h does not rest upon a con- 
necting plate but when the switch is rotated for the up motion, the 
terminal of h rests on plate v so that if the car switch is turned 
to the stop position, the current from wire h will pass to wire 
z and thus reverse the direction of rotation of the pilot 
motor, and return the switches to the stop position. If 
the car is running down, when the car switch is turned 
to the stop position, the current from wire h will pass to 
wire z and thus reverse the direction of rotation of the pilot 
motor, and return the switches to the stop position. If the car 
is running down, when the car switch is turned to the stop posi- 
tion, the wire h will ride over the plate u and thus the current 
will pass through the pilot motor through the up field and thus 
rotate the switches back to the stop position. In each case, as 
will be noticed, whenever the current flows through wire h it ener- 
gizes coil / and thus opens switch g. When the car is running 
up the current for the brake magnet passes from wire i through 
the switch which is energized by the main current flowing in wire q. 
When the car runs too far down, and closes the down limit switch, 
the motor circuit becomes closed through wires p, r and Zc, thus 
giving another path for the current generated by the motor arma- 
ture and thereby increasing the resistance to rotation. 

The controller for the Sprague drum machines is very similar 
to the one just described. It is operated by a pilot motor, and 
in so far as the controller switchboard is concerned looks the 
same. The only difference is that rendered necessary by the 
fact that in lowering as well as in raising the load, the motor is 
connected with the line. This requires a slight change in some 
of the wire connections. 



HANDBOOK ON ENGINEERING. 765 

The electrical parts of the Sprague elevators require very little 
attention other than to keep them clean and all the contacts bright 
and in proper adjustment, so that when moved a good contact 
may be made. Of the mechanical portion, the drum machines 
require about the same attention as other machines of this type. 
As to the screw machines, the part that requires most attention is 
the screw and the nut. As can be readily understood, if the nut 
were solid, the friction against the screw would be very great ; 
therefore, to reduce this friction, the nut is made so as to carry a 
large number of friction balls. These run in a groove cut in the 
side of a thread and roll between the thread and the screw and 
the thread in the nut. A tube is attached to the nut to provide a 
path through which the friction balls can pass from the end of the 
thread to the beginning, thus making an endless path in which 
they move. As these friction balls are subjected to a heavy pres- 
sure, there is more or less danger of their giving trouble and on 
that account the thread on the screw should be carefully examined 
and kept as clean and free from grit as possible. Under favorable 
conditions these screws run very well, the wear being trifling, but 
in some instances they are liable to cut badly, hence they should 
be closely watched. 

DIRECTIONS FOR THE CARE AND OPERATION OF THE 
ELECTRIC ELEVATORS. 

Whenever the attendant wishes to handle the machine to clean, 
adjust, repair or oil it, he should see that the current is shut off 
at the switch, and thus prevent all possibility of accident. 

Cleaning. — Keep the entire machine clean. Clean the com- 
mutator and other contacts and brushes carefully with a clean 
cloth and keep them free from grease and dirt. If the face of the 
rheostat on which the rheostat arm brushes work becomes burnt, 
clean with a piece of fine sand-paper (No. 0), or if necessary use 



766 HANDBOOK ON ENGINEERING. 

a fine file. Keep all contacts smooth. Try the rheostat arm 
when cleaning to be sure that it moves freely off contacts. 

Oiling. — Oil the drum shaft bearings with good heavy oil. 
Oil the worm and gear by filling the chamber around them with a 
mixture of two parts of good castor oil and one part good cylinder 
oil. Keep this chamber filled to the top of worm or mark on 
gauge glass, adding a little each day as it is used. The end 
thrust bearings of the machine are automatically oiled from this 
chamber. This should be drawn off every two or three months 
and replaced by fresh oil. Oil the motor bearings with dynamo 
oil. These are automatically oiled, but should occasionally be 
supplied with fresh oil. Lubricate the commutator, rheostat face, 
drum switch and contacts very sparingly with a cloth moistened 
with oil. Care should be taken not to supply too much oil to 
these parts. Keep the oil dash-pot, if any, sufficiently filled with 
oil to allow the rheostat arm to move quickly on to the first con- 
tact and to retard this movement beyond this contact. The best 
oil for this purpose is fish oil, or some thin oil that is not readily 
affected by changes in temperature. If an air dash-pot is used, 
keep it slightly oiled so as to keep the packing soft. Keep all 
parts of the elevator, including sheaves, guides, cables, etc., clean 
and well oiled. 

Operating. — Before switching the current on to the machine, be 
sure that the operating lever is in its central position. To ascend, 
draw the lever the full throw to the up . To descend , draw the lever 
the full throw to the down. To run at slow speed, bring the lever 
toward the center according to the speed desired. To stop, bring 
lever to slow speed when within four feet of landing, and to its 
central position when close to it. In this way, the operator can 
make accurate stops. When starting (machines on which the 
solenoid is used) if the current is admitted to the motor too 
rapidly, thereby starting the car with a jerk, or momentarily dim- 
ming the lights on the circuit, check the speed with which the 



HANDBOOK ON ENGINEERING. 767 

resistance is cut out of the armature circuit by slightly easing off 
the weight which acts in opposition to the core of the small 
solenoid. This solenoid controls a valve in the dash-pot and 
thereby regulates its speed in proportion to the current passing. 
If a governor starter is used and the current is admitted too 
rapidly, tighten the governor spring on the armature shaft, or 
close the vent in air dash-pot. If the car refuses to ascend 
with a heavy load, immediately throw the lever to the center 
and reduce the load, as in all probability it is greater than 
the capacity of the elevator. If it refuses to ascend with 
a light load, throw the lever to the center and have the 
fusible strip examined. If, in descending, the car should 
stop, throw the lever to the center and examine safeties, 
fusible strip and machine, and before starting, be sure that the 
cables have not jumped from their right grooves. If the car 
refuses to move in either direction, throw the lever on the center 
and have the fusible strips examined. Never leave the car with- 
out throwing the lever to the center. If the car should be stalled 
between floors, it can be either raised or lowered by raising the 
brake and running it by turning the brake-wheel by hand. Such 
a stoppage might be caused by the current being shut off at the 
station, undue friction in the machine, too heavy a load, fuses 
burnt out, or a bad contact of the switches, binding posts or elec- 
trical connections. If the car by any derangement of cables or 
switch cannot be stopped, let it make its full trip, as the auto- 
matic stop will take care of it at either end of the travel. The 
bearings should be examined occasionally to insure no heating 
and proper lubrication. 

General dir ections* — Have the machine examined occasionally 
by someone well posted in electric motors and elevators. The 
attendant should inspect the machine often. All brushes and 
switches should be sufficiently tight to give a good contact, but 
no tighter. None of the brushes should spark when in their 



768 HANDBOOK OX ENGINEERING. 

normal position. When the brushes become burnt dress with 
sandpaper or file, or, if necessary, replace with new ones. If 
brushes spark, dress with sandpaper or file to a good bearing, 
and, if necessary, set up springs, but do not make the ten- 
sion such as to interfere with their ready movement. Adjust 
commutator brushes gradually for least sparking. These should 
be close to the central position. Contacts and brushes should 
be kept clean and smooth and lubricated sparingly. While 
replacing a fusible strip, be sure that main switch is open, and be 
careful not to touch the other wire with your tool or otherwise, as 
such contact would be dangerous. Never put in a larger fuse 
than the one burnt. Inspect the worm and worm-wheel occasion- 
ally through hand-holes in casing, to see that they are well lubri- 
cated, and that no grit gets into the oil. They should show no 
wear. The stuffing box on the worm shaft should be only tight 
enough to keep the oil from leaking out of the worm chamber. 
Be sure that all parts are properly lubricated, and that none of 
the bearings heat. To make sure that the car and machinery run 
freely, lift brake lever and then rotate worm shaft by pulling on 
the brake wheel. The empty car should ascend without any exer- 
tion. Keep operating cables properly adjusted. Open main 
switch when the elevator is not in service. 



HANDBOOK ON ENGINEERING. 



769 



CHAPTER XXVI. 

HYDRAULIC ELEVATORS. 

The pttfpose of these pages is to furnish such instructions and 
information as will be of use to engineers in the handling of eleva- 
tor machinery. To accomplish this end, cuts and sectional views 
of cylinders and valves of the different types of elevator machin- 
ery made by the different elevator companies, are herein produced, 




so as to make the different elevators plain to the engineer. It 
must be borne in mind that the one point of paramount impor- 
tance for the successful operation of an elevator is proper care 
and management ; a lack of thorough knowledge of the machine 
and lack of attention in this respect shortens the life of the ma- 
chine and often makes extensive repairs necessary. 

HOW TO PACK HYDRAULIC VERTICAL CYLINDER 
ELEVATORS. 

Packing vertical cylinder piston from top. — Rim the car 
to the bottom and close the gate valve in the supply pipe. Open 
the air cock at the head of the cylinder, and also keep open the 



770 



HANDBOOK ON ENGINEERING. 




Showing how to set therope on the lever elevator ; the slieaveg 
want to be on e center of the travel, as shown. 



HANDBOOK ON ENGINEERING. 771 

valve in the drain pipe from the side of the cylinder long enough to 
drain the water in the cylinder down to the level of the t023 of the 
piston. Now remove the top head of the cylinder, slipping it and 
the piston rods up out of the way, and fasten there. If the piston 
is not near enough to the top of the cylinder to be accessible, attach 
a rope or small tackle to the main cables (not the counter-balance 
cables) a few feet above the car, and draw them down sufficiently 
to bring the piston within reach. Remove the bolts in the piston 
follower by means of the socket wrench furnished for that pur- 
pose. Mark the exact position of the piston follower before re- 
moving it, so that there will be no difficulty in replacing it. On 
removing the piston follower you will find a leather cup turned 
upwards, with coils of |-inch square duck packing on the outside. 
This you will remove and clean out the dirt ; also clean out the 
holes in the piston through which the water acts upon the cup. 
If the leather cup is in good condition, replace it, and on the 
outside place three new coils of |-inch square duck packing, being- 
careful that they break joints, and also that the thickness of the 
three coils up and down does not fill the space by J inch, as in 
such case the water might swell the packing sufficiently to cramp 
it in this space, thus destroying its power to expand. If too 
tight, strip off a few thicknesses of canvas. Replace the piston 
follower and let the piston down to its right position. Replace 
the cylinder head and gradually open the gate valve in the supply 
pipe, first being sure that the operating valve is on the down 
stroke or it is so the car is coming down. As soon as the air has 
escaped before closing the air cock to make sure the air is all out 
of the cylinder, make a few trips, and the elevator is ready to 
run. 

Packing the vertical cylinder valves* — To pack the valve, 
run the car to the bottom and close the gate valve in the supply 
pipe. Then throw the operating valve for the car to go up, open 
the air cock at the head of the cylinder and the valve in the drain 
pipe at the bottom, and the water will drain out of the cylinder. 



772 



HANDBOOK ON ENGINEERINGo 




Section of Elevator Cylinder and 
Valve Showing Working Parts. 




OTIS VCRTICAL HYDRAULIC PASSENGER AND FREIGHT MACHINE 

A shows the position of the valve at rest. B shows the position of the valve when the car is going 
up or hoisting. C shows the position of the valve when the car is coming down or lowering. 



HANDBOOK ON ENGINEERING. 773 

When the cylinder is empty, reverse the valve for the car to run 
down, so as to let the water out of the circulating pipe. In cases 
of tank pressure, where the level of the water in the lower tank is 
above the bottom of the cylinder, the gate valve in the discharge 
pipe will have to be closed as soon as the water in the cylinder is 
on a level with that in the tank, allowing the rest to pass through 
the drain pipe to the sewer. As soon as the water has all drained 
off, take off the valve cap and remove the pinion shaft and sheave, 
marking the position of the sheave and the relation which the 
teeth on the pinion bear to the teeth on the rack before removing. 
You can now take out the valve plunger and put the new cup 
leather packings on in the same position as you find the old ones. 
Replace all the parts as first found. Before refilling the cylinder, 
close the valves in the drain pipes, but leave the air cock at the 
head of the cylinder open and be careful that the operating valve 
is in position for the car to go down. Gradually open the gate 
valve in the supply pipe. When the cylinder has filled with water 
and the air has escaped, close the air cock and open the gate 
valve in the discharge pipe. 

Packingf piston tods* — Close the gate valve in the supply pipe. 
Remove the followers and glands to the stuffing boxes and clean 
out the old packing. Repack with about eight turns of J inch flax 
packing to each rod, and replace glands and followers. Screw 
down the followers only tight enough to prevent leaking. 

Packin§: Otis Vertical Piston from bottom. — Remove the 
top stop-button on hand rope and run the car up until the piston 
strikes the bottom head in cylinder. Secure the car in this posi- 
tion by passing a strong rope under the girdle or crosshead and 
over the sheave timbers. When secured, close the gate valve in 
the supply pipe, open the air cock at the head of the cylinder, and 
throw the operating valve for the car to go up. Also open the 
valve in the drain pipe from the side of the cylinder, and from 
the lower head of the cylinder, thus allowing the water to drain 



774 HANDBOOK ON ENGINEERING. 

out of the cylinder. When the cylinder is empty, throw the valve 
for the car to descend in order to drain the water from the cir- 
culating pipe. In case of tank pressure, where level of water in 
lower tank is above the bottom of the cylinder, the gate valve in 
the discharge pipe will have to be closed as soon as the water in 
the cylinder is on a level with that of the tank, allowing the rest 
to pass through the drain pipe to the sewer. When the water is 
all drained off, remove the lower head of the cylinder, and the 
piston will be accessible. Remove the bolts in the piston follower 
by means of the socket wrench, which is furnished for that pur- 
pose. Before removing the piston head, mark its exact position, 
then there will be no difficulty in replacing it ; also be careful and 
not let the piston get turned in the cylinder, so as to twist the 
piston rods. On removing the piston follower, you will find a 
leather cup turned upwards, with coils of | in. square duck 
packing on the outside. This you will remove and* clean out the 
dirt ; also clean out the holes in the piston, through which the water 
acts upon the cups. If the leather cup is in good con- 
dition, replace it and on the outside place three new coils of 
I inch square duck packing, being careful that they break joints 
and also that the thickness of the three coils up and down does 
not fill the space by i inch, as in such case the water might swell 
the packing sufficiently to cramp it in this space, thus destroying 
its power to expand. If too tight, strip off a few thicknesses of 
canvas. Replace the piston follower and cylinder head, and the 
cylinder is ready to refill. Close the valves in the drain pipes, 
leave the air cock open at the head of the cylinder and the oper- 
ating valve in the position to descend, and open gate valve in the 
discharge. Slowly open the gate valve in the supply pipe, allow- 
ing the cylinder to fill gradually and the air to escape at the head 
of the cylinder. When the cylinder is full of water, leave the air 
cock open and put the operating valve on the center. The car can 
then be untied, the stop button can be reset, and the elevator is 
ready to use. Make a few trips before closing the air valve. 



Hj\ndbook on engineering. 



775 




The above cut is the Auxiliary Valve for Crane Hydraulic 
Passenger Elevators. 

The operation of this valve is explained as follows: D repre- 
sents the supply inlet ; JJ, the discharge outlet ; F^ the opening 



776 HANDBOOK ON ENGINEERING. 

to the cylinder ; 6r, the pilot valve ; jET, the pilot valve supply 
pipe to the motor cylinder ; JSf and J, the attachment by which 
the valve is operated. Fig. 1 represents the valve on centers, or 
the car at rest at any floor between limits of travel. It will be 
noticed in cut that the plunger heads A and B are on either side 
of the central opening. The water is then entirely cut off from 
the machine and the pilot valve covers the port C. To start the 
car up, water is admitted to the cylinder /through the inlet D. 
This is accomplished by pushing on the connection in which 
opens the port C in the pilot valve G, allowing the water in the 
motor cylinder I to flow into the discharge E. The flow is regu- 
lated by the screw K. The pressure in the motor cylinder / 
being relieved, the valve plunger moves to the right under the 
difference in pressure upon the plunger A and L, L being of 
smaller diameter than A. Supply is thus admitted to the cylin- 
der through F. To start the car down, pull on the connection J. 
The port C in the pilot valve chest is opened, allowing water 
from the pilot supply H to flow into the motor cylinder I. The 
pressure on head forces the plunger B to move to the left. Water 
is thus allowed to j)ass out from F to the discharge E. If a 
slow movement of the car is desired, connection J \^ removed to 
the right or left for either up or down, and only enough to open 
the main valve slightly to give the desired speed. This speed is 
maintained by the lever being moved on its fulcrum P, thus 
necessitating the valve G covering port C. 

AUTOriATIC STOP VALVE. 

The stop valve M is opened automatically by the machine as 
the elevator starts from the top or bottom landing, giving free flow 
of water to the cylinder. As the car reaches the upper or lower 
limit of travel, the valve is automatically closed, so that the car 
stops gradually at the terminals. 



HANDBOOK ON ENGINEERING. 777 

OTIS GRAVITY WEDGE SAFETY. 

i^ Under the car is a heavy bardwood safety plank, on each 
end of which is an iron adjustable jaw, inclosing the guide on 
the guide post. In this jaw is an iron wedge, withheld from con- 
tact with the guide in regular duty. Under the wedge is a rocker 
arm, or equalizing bar, with one of the lifting cables attached 
independently at each extremity. The four lifting cables, after 
being thus attached, pass over a wrought iron girdle at the top 
of the car. Each cable carries an equal strain, and the breakage 
of any one cable puts the load on the other cables, which throws 
the rocker out of equilibrium and forces the wedges on both sides 
instantly and immovably between the iron jaws of the safety 
plank and the side of the guides, stopping the car. It may be 
raised to any position by the unbroken cables, though it cannot 
be lowered until a new cable is put on. 

2* Any cable will always stretch before it breaks, which will 
throw the equahzing safety-bar out of equihbrium and force the 
wedges on both sides into position. No other safety device will 
give warning in advance. 

CARE OF HALE ELEVATORS. 

Keep the guide springs on the girdle above, and the safet;^ 
plank below the car adjusted, so that the car will not wabble, but 
not tight enough to bind against guides. When cables are draw- 
ing alike, the equalizing bars on a passenger elevator should be 
horizontal, and the set screws free from contact with the finger 
shaft, but adjusted so that one of them will come in contact 
with the finger shaft when the equalizing bar is tipped a certain 
amount either way. If the safety wedges should be thrown in, 
or rattle, when descending, the cause would be from the stretch- 
ing or breaking of one of the cables, the action of the governor, 
or from weakness of either the spring on the finger shaft, 



778 HANDBOOK ON ENGINEERING. 

safety-wedge or gummy guides. In the first case, if occa- 
sioned by the cable stretching, the cable should be examined 
thoroughly, and if it shows weakness, a new one put on, 
otherwise, it can be shortened up, as stated above. In the sec- 
ond case, the car had probably attained excessive speed and the 
governor simply performed its proper function. In the third 
case, new springs should be put on and the guides kept clean, 
for it often happens that the guides are so dirty that the springs 
cannot well prevent the wedges catching. Ail the safeties should 
be kept clean and in good order, so that they will quickly respond 
when called upon to perform their duty. To loosen the wedges 
when thrown in, throw the valve for the car to ascend. If the 
wedges are thrown in above the top landing, remove the button 
on the hand cable and run the car up until the piston strikes the 
bottom of the cylinder. If this is not sufficient to loosen the 
wedges, the car will have to be raised by a tackle. Keep all nuts 
properly tightened. 

If traveling" or auxiliary sheave bushing is worn so that sheave 
binds, or the bushing is nearly worn through, turn it half round, 
and thus obtain a new bearing. If it has been once turned put 
in a new bushing. See that the piston rods draw alike. If the}- 
do not, it can be discerned by trying to turn the rods with the 
hand, or by a groaning noise in the cylinder. However, this 
groaning may also be caused by the packing being worn out, in 
which case the car would not stand stationary. See that all 
supports remain secure and in good condition. 

WATER FOR USE IN HYDRAULIC ELEVATORS. 

In hydraulic elevator service little heed is usually given to the 
quality of water with which the system is operated. Much loss 
of power by friction and many dollars spent annually in repairs 
can be avoided by a little thought and action on this subject. In 
order to j^rove the truth of this statement, one has only to obtain 



HANDBOOK ON ENfJTNEERING. 779 

two samples of water, oue of soft water and the other of what is 
commonl}' known as hard water. For example, take rain water 
as the first sample and water from the well as the second. Now 
rub your hands briskly together while holding them immersed in 
one, and then in the other of these samples. You will instantly 
realize that the quality of water used in elevator service has much 
to do with the efficiency of the hydraulic machinery. Water from 
the service i3ipes of the city water-works always contains more or 
less sand and other gritty substances, in suspension, and this grit 
acts much the same on the packing and metal parts of the appar- 
atus as does a sand blast. Some engineers, having realized the 
evil effects of water in the state that it is generally used, have 
attempted to remedy the matter by replacing the water which is 
lost by leakage or evaporation by the addition of the water which 
is discharged from the steam traps of the plant ; and as this has 
been distilled, it is almost chemically pure — thus the man who 
uses distilled water in an elevator system instead of the water 
containing grit, is simply get ding out of one difficulty into 
another. 

It is a well^nown fact in chemistry that pure water is a solvent 
for every known substance, and will especially attack iron to a 
large degree. Whenever it is practicable, the water for elevator 
use should be passed through a filter to remove grit before 
being allowed to pass into the surge tank. In many cases, 
however, it would be difficult for the engineer to convince the 
owner of the advisability of buying and installing a filter for this 
purpose. A simple and somewhat inexpensive remedy is within 
reach of all — the plentiful use of soap will obviate many of the 
evil effects of hardness of the water, will double the life of the 
packing, will reduce the loss by friction, and will, to a large 
extent, prevent the chattering of the pistons, making the elevators 
run much smoother. In laboratory practice, the degree of hard- 
ness or softness of water is determined by the amount of pure 



780 



HANDBOOK OX ENGINEERING. 




PIANDBOOK ON ENGINEERING. 781 

soap that is uecessaiy to mix with the water to form a lather, or 
to precipitate a certain quantity of carbonate of lime and other 
substances. This same action, on a larger scale, takes place 
when soap is introduced into an elevator tank, and while the oily 
portion of the soap forms an emulsion with the water, of great 
lubricating properties, the gritty matter is precipitated and can 
be gotten rid of through means of a blow-off in the bottom of the 
tank. The cheapest and most convenient form in which to obtain 
soap for this purpose, is the soap powder extensively manufac- 
tured by various firms and which can be purchased for about four 
cents per pound. In a plant of six elevators, with usually a 
storage capacity of some 8,000 gallons, it is a good practice to 
use about twenty pounds of this soap each week. The soap 
should be at first dissolved in about ten times its weight of boil- 
ing water, and when cold it will form a stiff soft soap. The 
practice of putting in the refuse oil collected from the drip pans is 
of little value ; it will not mix with the water, but floats on the 
surface. It rarelj^ gets low enough to enter the suction pipes of 
the pumps, and has little or no tendency to precipitate the solid 
matter that is held in suspension in the water. 

If car settles, the most probable cause is that the valve or pis- 
ton needs repacking. If packing is all right, then the air valve 
in the piston does not properly seat. If the car springs up and 
down when stopping, there is air in the cylinder. When there 
is not much air, it can often be let out by opening the air cock 
and running a few trips, but when there is considerable air, 
run the car to near the bottom, placing a block underneath for 
it to rest upon, then place the valve for the car to descend. 
While in this position, open the air cock and allow the air to 
escape. This may have to be repeated several times before the 
air is all removed. 

Keep the cylinder and connections protected from frost. 
Where ex])osed, the easiest way to protect the cylinder is by an 



782 HANDBOOK ON ENGINEERING. 

air-tight box, open at the bottom, at which point keep a gas jet 
burning during cold weather. Where there is steam in the build- 
ing, run a coil near the cylinder. Keep stop buttons on hand cable 
properly adjusted, so that the car will stop at a few inches beyond 
either landing, before the piston strikes the head of the cylinder. 
Regulate the speed desired for the car by adjusting the back stop 
buttons, so that the valve can only be opened either way suflS- 
ciently to give this speed. Occasionally try the governor to see 
that it works properly. Keep the machinery clean and in good 
order. 

ELEVATOR INCLOSURES AND THEIR CARE. 

Elevator inclosures, while intended for protection to passen- 
gers, are often carelessly neglected and are often a source of 
danger, unless looked after and taken care of in a proper manner. 
It is of the utmost importance that no projection of any kind 
shall extend into the doorways for clothing of passengers to 
catch on, thus endangering their lives. The door should move 
freely to insure their action at the touch of the operator. See 
that all bolts and screws are tight, and replace at once all that 
fall out, otherwise, the doors and panels may swing into the path 
of the elevator cage and be torn off, and probably injure some 
one, thus placing the owner liable to damages. Elevator doors 
that are automatic in their closing are the best, but all operators 
should be held strictly responsible for accidents occurring from 
the carelessness of leaving doors open. All inclosures should be 
equipped with aprons above the doors to the ceiling and as close 
to the cage as possible, to prevent passengers from falling out or 
extending their person through to be caught by ceilings or beams 
in the elevator shaft. As a rule, proprietors of buildings take a 
pride in keeping their inclosures and cars in a neat condition, as 
they are considered an ornament to the building for the purpose 
for which they are intended, and no expense is spared in the 



HANDBOOK ON ENGINEERING. 



783 



line of art; so it is recommended that they be kept free from 
dampness. Dust with a feather duster and use soft rags for 
cleaning. Never use any gritty substance, soaps or oils. If they 
become damaged, have the maker repair and relacquer them. 

STANDARD HOISTING ROPE WITH 19 WIRES 
TO THE STRAND. 





, ^ 1 


2 


S o o : 

3 a n i 


5 



Weight per 
foot in lbs. I 

of rope 
with hemp 

center, i 



1ons"of" load in tons 
2000 lbs. I ^,,^\^^^ 



Circumfer- 
ence of new 
Manilla 
rope of 
equal 
strength. 



Minimum 

size of 

drum or 

sheave in 

feet. 



1 


2i 


2 


2 


3 


11 


4 


n 


5 


u 


5.i 


n 


6 


H 


7 


U 


8 




9 


i ■ 


10 


^ 1 


m 


t ! 


m. 


A 1 


101 


h 


lOa 


1-6 


10^ 


1 



6 

5^^ 

5 

41 

4§ 

4 

H 

3i 

21 

2i 

2 

If 

H 
If 
U 



8.00 
6.30 
5.25 
4.10 
3.65 
3.00 
2.50 
2.00 
1.58 
1.20 
0.88 
0.66 
0.44 
0-35 
0.29 
0.26 



74 

65 

54 

44 

39 

33 

27 

20 

16 

11.50 
8.64 
5.13 
4.27 
3.48 
3.00 
2.50 



15 
13 
II 

9 
8 

eh 
5h 



n 
u 



14 
13 
12 
11 
10 
H 

n 

6h 

5h 

4i 

31 

3^ 

3 

2| 

2h 



13 

12 

10 
Sh 
Ih 
7 

6 

H 

4i 

4 

Sh 

21 

2i 

2 

H 



Operating Cable or Tiller Rope, | in. diam. 
[ in. diam. 



I in. diam.; J^ in. diam. 



Cables^ and how to care for them* — Wire and hemp ropes of 
same strength are equally pliable. Experience has demonstrated 
that the wear of wire cables increases with the speed. Hoisting 
ropes are manufactured with hemp centers to make them more 
pliable. Durability is therein^ increased where short bending 



<'84 HANDBOOK ON ENGINEERING. 

occurs. All twisting and kinkiug of wire rope should be avoided. 
Wire rope should be run off by rolling a coil over the ground 
like a wheel. In no case should galvanized rope be used for 
hoisting purposes. The coating of zinc wears off very quickly 
and corrosion proceeds with great rapidity. Hoisting cables 
should not be spliced under any circumstances. All fastenings 
at the ends of rope should be made very carefully, using only 
the best babbitt. All clevises and clips should fit the rope 
perfectly. Metal fastenings, where babbitt is used, should be 
warmed before pouring, to prevent chilling. Examine wire ropes 
frequently for broken wires. Wire hoisting ropes should be con- 
demned when the wires (not strands) commence cracking. Keep 
the tension on all cables alike. Adjust with draw-bars and turn- 
buckles provided. 

Leather cup packings for valves* — Leather for cups should 
be of the best quality, of an even thickness, free from blemish 
and treated with a water-proof dressing. The cups should be 
of sufficient stiffness to be self-sustaining when passing over per- 
forated valve lining When ordering cups, the pressure of water 
carried should be specified, as the stiff cups intended for high- 
23ressure would not set out against the valve lining when low pres- 
sure is used. 

Water* — Water for use in hydraulic elevators should be per- 
fectly clear and free from sediment. A strainer should be placed 
on the supply pipe and water changed every three months, and 
the system washed and flushed. 

Closingf down elevators* — If an elevator is to be shut down 
for an indefinite period, run the car to the bottom and drain off 
the water from all parts of the machine ; otherwise, a freeze is 
likely to burst some part of the machinery. It the machine is of 
the horizontal type, grease the cylinder with a heavy grease ; if 
vertical, the rods should be greased. Oil cables with raw linseed 
oil. 



HANDBOOK ON ENGINEERING. 785 

LUBRICATION FOR HYDRAULIC ELEVATORS. 

The most effectual method of lubricating the internal parts of 
hydraulic elevator j^lants where pump and tanks are used, is to 
carry the exhaust steam drips from the foot of the pump exhaust 
pipe to the discharge tank, thus saving the distilled water and 
cylinder oil. This system is invaluable when water holding in 
solution minerals is used, as these minerals greatly increase cor- 
rosion. Horizontal machines operated by city pressure are best 
lubricated with a heavy grease applied either mechanically or by 
means of a piece of waste on the end of a pole. The former 
method serves as a constant lubricator, while in the latter case, 
greasing is often neglected, and in consequence packing lasts but 
a short time. 

Lubrication of worm gearing. — Oils with a body, such as 
cylinder and castor oils, are best suited to the purpose. A com- 
position of two parts castor to one part cylinder oil of the very 
best quality, makes a desirable lubricant, for the following rea- 
sons : cylinder oil being heavy with ample body, on becoming- 
warm runs freely to the point of contact between the worm and 
the gear and lubricates readih^ On the other hand, castor oil 
when cool, or only slightly warm, retains its body and makes an 
excellent lubricant. Upon becoming heated, castor oil thickens, 
thus rendering it objectionable. By the combination, efficient 
lubrication is obtained at all temperatures. 

Lubrication of cables* — A good compound for preservation 
and lubrication of cables is composed of the following : Cylinder 
oil, graphite, tallow and vegetable tar, heated and thoroughly 
mixed. Apply with a piece of sheepskin with wool inside. To 
prevent wire rope from rusting, apply raw linseed oil. 

Lubrication of guides* — Steel guides should be greased with 
good cylinder oil. Grease wood strips with No. 3 Albany grease 
or lard oil. Clean guides twice a month to prevent gumming. 



786 HANDBOOK ON ENGINEERING. 

Lubrication of overhead sheave boxes* — In summer use a 
heavy grease. In winter, add cylinder oil as required. 

BELTS AND HOW TO CARE FOR THEM. 

The work required of an elevator belt is most severe and we 
might say extraordinary character, running as it does over a large 
to a small pulley and beneath an idler, so situated as to give the 
small pulley as much belt surface as possible. The belt runs 
forward and backward as the cage descends and ascends, thereby 
causing a certain amount of slip. It is imperative that a belt 
performing such service should be of the very best quality. The 
following are the specifications : The stock should be strictly 
pure oak-tanned, cut in such a manner that the center of the hide 
will form the center of the belt. Each piece should have all 
stretch thoroughly removed. The belt should be short lap, none 
of the pieces to exceed 4' 2" in length, including the laps. Lock 
lap should be made, which makes a perfect splice. Under no 
circumstances should a straight lap be used. The cement should 
be of the very best quality and pliable to such an extent that it 
will allow for the short turn taken by the belt in passing under 
the idler and around the small pulley. As a precaution against 
laps coming apart from accident or other cause, belts should be 
riveted, as the rivets will hold lap together until defect may be 
seen and remedied. Owing to the high speed, laced belts should 
never be used, as the laces are sure to be cut by running over the 
small pulleys. Castor oil makes a very reliable dressing for 
belts. It renders them pliable, thus improving the adhesive 
qualities. 

USEFUL INFORMATION. 

To find leaks in elevator pressure tanks in which air is con- 
fined, paint round the rivet heads with a solution of soap and the 
leak will be found wherever a bubble or suds appear. To ascer- 
tain the number of oallons in cylinders and round tanks, multi- 



HANDBOOK ON ENGINEERING. 



787 



ply the square of the diameter in inches by the height in inches 
ply the square of the diameter in inches by the height in inches 
and the product by .0034 = gallons. Weight of round wrought 
iron : Multiply the diameter by 4, square the product and divide 
by 6 =rr: the weight in pounds per foot. To find the weight of a 
casting from the weight of a pine pattern, multiply one pound of 
pattern by 16.7, for cast-iron, and by 19 for brass. Ordinary 
gray iron castings = about 4 cubic inches to the pound. 

Water* — -A- gallon of water (U. S. Standard) contains 231 
cu. in. and weighs 8^ lbs. A cubic foot of water contains 7J gal- 
or 1728 cu. in. and weighs 62.425 lbs. A " Miner's inch" is a 
measure for the flow of water and is the amount discharged 
through an opening 1 inch square in a plank 2 in. in thickness, 
under a head of 6 in. to the upper edge of the opening ; and this 
is equal to 11.625 U. S. gal. per minute. The height of a 
column of fresh water, equal to a pressure of 1 lb. per sq. in., is 
2.304 feet. A column of water 1 ft. high exerts a pressure of .433 
lbs. per sq. in. The capacity of a cylinder in gallons is equal to 
the length in inches multiplied by the area in inches, divided by 
231 (the cubical contents of one U. S. gal. in inches). The 
velocity in feet per minute, necessary to discharge a given volume 
of water in a given time, is found by multiplying the number of 
cu. ft. of water by 144 and dividing the product by the area of 
the pipe in inches. 



Decimal Equivalents of an Inch. 



1-16 


1-8 


3-16 


1-4 


516 


3-8 


. 7-16 


1-2 


.0625 


.125 


.1875 


.25 


.3125 


.375 


.4375 


.5 


9-16 


5-8 


11-16 


3-4 


13-16 


7-8 


15-16 




.5626 


.625 


.6875 


.75 


.8125 


.875 


-9375 





788 HANDBOOK ON ENGINEERING. 



CHAPTER XXVII. 

THE DRIVING POWER OF BELTS. 

The avetag-e strain or tension at which belting should be run, 
is claimed to be 55 pounds for every inch in width of a single belt, 
and the estimated grip is one-half pound for every square inch of 
contact with pulley, w^hen touching one-half of the circumference 
of the pulley. For instance a belt running around a 36-inch pul- 
ley would come in contact with one-half its circumference, or 56i 
inches, and allowing a half-pound per inch, would have a grip 28J 
pounds for each inch of width of belt. 

HECHANICAL PROBLEMS AND RULES. 

Problem 1 . To find the circumference of a circle or a 
pulley : — 

Solution. Multiply the diameter by o.l41() ; or, as 7 is to 22 
so is the diameter to the circumference. 

Problem 2. To compute the diameter of a circle or pulley: — 

Solution. Divide the circumference by 3.1416; or multiply 
the circumference by .3183 ; or as 22 is to 7, so is the circumfer- 
ence to the diameter, equally applicable to a train of pullej^s, the 
given elements being the diameter and the circumference. 

Problem 3. To find the number of revolutions of driven pulley, 
the revolution of driver, and diameter of driver and driven being- 
given : — 

Solution. Multiply the revolutions of driver hy its diameter, 
and divide the product l\v the diameter of driven. 



HANDBOOK ON ENGINKEKING. 789 

Problem 4. To compute the diameter of driven pulley for any 
desired number of revolutions, the size and velocity of driver 
being known : — 

Solution. Multiply the velocity of driver by its diameter and 
divide the product by the number of revolutions it is desired the 
driven shall make. 

Problem 5. To ascertain diameter of driving pulley : — 

Solution. Multiply the diameter of driven by the number of 
revolutions you desire it shall make, and divide the product by 
the number of revolutions of the driver. 

6. Rule for finding: length of belt wanted: Add the diame- 
ters of the two pulleys together, divide the result by two, and 
multiply the quotient by 3 1/7. Add the product to twice the 
distance between the centers of the shafts, and you have the 
length required. 

For Calculating the Nuimbpzk of Horse-Power Which a Belt 
Will Transmit^ Its Velocity and the Number op Square Inches 
IN Contact With the Pulley Being Known. 

Divide the number of square inches of belt in contact with the 
pulley by two, multiply this quotient by velocity of the belt in 
feet per minute and divide the product by 33,000 ; the quotient is 
the number of horse-power. 

Example. — A 20-inch belt is being moved with a velocity of 
2,000 feet per minute, with six feet of its length in contact 
with the circumference of a four-foot drum ; desired its horse- 
power. 20 X 72 equal 1,440, divided by two, equals 720 x 2,000 
equal 1,440,000 divided by 33,000 equal 43| horse-power. 

Rule for finding width of belt, when speed of belt in feet per 
minute and horse power wanted are given : — 

For single belts* — Divide the speed of belt by 800. The horse- 
power wanted divided by this quotient, willjgive the width of 
belt required. 



790 HANDBOOK ON ENGINEERING. 

Examjjle. — Required the width of single belt to transmit 100 
horse-power. Engine pulley 72" in diameter. Speed of engine, 
220 revolutions per minute. 

800) 4146 (speed of belt per minute). 

5.18)100.00 (horse-power wanted). 

19" width of belt required. 

For double belts« — Divide the speed of belt in feet per minute 
by o60. Divide the horse-power wanted by this quotient for the 
width of belt required. 

Example. — Required the width of double belt to transmit 500 
horse-power. Engine pulley 72" in diameter. Speed of engine, 
220 revolutions per minute. 

560)4146 (speed of belt per minute). 

7.4)500.00 (horse-power wanted). 

67|" width of belt required. 

EXTRACTS FROM ARTICLES ON BELTS. 

BY R. J. ABERNATHEY. 

Although there is not near as much known in general about 
the power of transmitting agencies as there should be, still it 
seems that almost any other method or means is better understood 
than belts. 

One of the chief difficulties in the way of a better knowledge of 
the belting problem, is the relation that belts and pulleys bear to 
each other. The general supposition, and one that leads to many 
errors, is that the larger in diameter a pulley is, the greater its 
holding capacity — the belt will not slip so easily, is the belief. 
But it is merely a belief, and has nothing to sustain it, unless it 
be faith, and faith without work is an uncertain factor. I would 



HANDBOOK ON ENGINEEKING. 791 

like here to impress upon the minds of all interested, the following 
immutable principles or law : — 

1. The adhesion of the belt to the pulley is the same — the arc 
or number of degrees of contact, aggregate tension or weight 
being the same — without reference to width of belt or diameter 
of pulley. 

2. A belt will slip just as readily on a pulley four feet in diam- 
eter, as it will on a pulley two feet in diameter, provided the 
conditions of the faces of the pulleys, the arc of contact, the ten- 
sion, and the number of feet the belt travels per minute are the 
same in both cases. 

3. A belt of a given width and making two thousand, or any 
other given number of feet per minute, will transmit as much 
power running on pulleys two feet in diameter as it will on 
p'ulleys four feet in diameter, provided the arc of contact, tension 
and conditions of pulley faces all be the same in both cases. 

It must be remembered, in reference to the first rule, that when 
speaking of tensions, that aggregate tension is never meant unless 
so specified. A belt six inches wide, with the same tension, or 
as taut as a belt one inch wide, would have six times the aggre- 
gate tension of the one inch belt. Or it would take six times 
the force to slip the six inch belt as it would the one inch. I 
prefer to make the readers of this, practical students. I want 
them to learn for themselves. Information obtained in that way 
is far more valuable, and liable to last much longer. 

In order that the reader may more fully understand whether 
or not a large pulley will hold better than a small one, let him 
provide a short, stout shaft, say three or four feet long and two 
inches in diameter. To this shaft firmly fasten a pulley, say 
12 in. in diameter, or any other size small pulley that may be 
convenient. The shaft must then be raised a few feet from the 
floor and firmly fastened, either in vices, or by some other means, 
so that it will not turn. It would be better, of course, to have 



792 HANDBOOK ON ENGINEERING. 

a smooth-faced iron pulley, as such are most generally used. So 
far as the experiment is concerned, it would make no difference 
what kind of a pulley was used, provided all the pulleys experi- 
mented with be of the same kind, and have the same kind of face 
finish. When the shaft and pulleys are fixed in place, procure a 
new leather belt and throw it over the pulley. To one end of the 
belt attach a weight, equal, say, to forty pounds — or heavier, if 
desired — for each inch in width of belt used ; let the weight 
rest on the floor. To the other end of the belt attach another 
weight, and keep adding to it until the belt slips and raises the 
first weight from the floor. After the experimenter is satisfied 
with plajing with the 12 in. pulley, he can take it off the 
shaft and put on a 24 in., a 3(3 in., or any other size he may 
wish ; or, what is better, he can have all on the shaft at the 
same time. The belt can then be thrown over the large pulley 
and the experiment repeated. It will then be found if pulley 
faces are alike, that the weight which slipped the belt on the 
small pulley will also slip it on the large one. The method 
shows the adhesion of a belt with 180 degrees contact, but as the 
contact varies greatly in practice, it is well enough to understand 
what may be accomplished with other arcs of contact. But, after 
all, many are probably at a loss how to account for some obser- 
vations previously made. They have noticed that when a belt at 
actual work slipped, an increase in the size (diameter) of the 
puUej's remedied the difl&culty and prevented the slipping. 

A belt has been known to refuse to do the work allotted to it, 
and continue to slip over pulleys two feet in diameter, but from 
the moment pulleys were changed to three feet in diameter there 
was no further trouble. These observed facts seem to be at 
variance with and to contradict the results of the experiments 
that have been made. All, however, may rest assured that it is 
only apparent, not real. 

The resistance to slippage is simply a unit of useful effect (or 



HANDBOOK ON ENGINEERING. 793 

tliut wbicli call be converted into useful effect). The magnitude 
of the unit is in jjroportion to the tension of the belt. The sum 
total of useful effect depends upon the number of times the unit 
is multiplied. A belt 6 inches wide and having a tension equal 
to 40 lbs. per inch in width, and traveling at the rate of 1 foot 
per minute, will raise a weight of 240 lbs. 1 foot high per minute. 
If the speed of the belt be increased to 136.5 feet per minute, it 
will raise a weight of 33,000 lbs. per minute, or be transmitting 
1 horse-power. The unit of power transmitted by a belt is rather 
more than its tension, but to take it at its measured tension is at 
all times safe, and 40 to 45 lbs. of a continuous working strain is 
as much, perhaps, as a single belt should be subjected to. A 
little reflection will now convince the reader that a belt transmits 
power in proportion to its lineal speed, without reference to the 
diameter of the pulleys. Having arrived at that conclusion, it is 
then easy to understand why it is that a belt working over 36-inch 
pulley will do its work easy, when it refused to do it and slipped 
on 24-inch pulleys. If the belt traveled 800 feet per minute on 
the 24-inch pulleys, on the 36-inch it would travel 1,200 feet, 
thus giving it one-half more transmitting power. If, in the first 
instance, it was able to transmit but 8 horse-power, in the second 
instance it will transmit 12 horse-power. All of which is due to 
the increase in the speed of the belt and not to the increase in the 
size of the pulleys ; because, as has been shown, the co-efficient 
of friction, or resistance to slippage, is the same on all pulleys 
with the same arc of belt contact. 

There is no occasion for elaborate and perplexing formulas and 
intricate rules. They serve no useful purpose, but tend only to 
mystify and puzzle the brain of all who are not familiar with the 
higher branches of mathematics, — and it is the fewest number 
of our every-day practical mechanics who are so familiar. In all, 
or nearly all treatises on belting, the writer will tell you that at 
600, 800 or 1,000 feet per minute, as the case may be, a belt one 



794 HANDBOOK ON ENGINEERING. 

inch wide, will transmit one horse-power ; and yet, when we come 
to apply their rules in practice, no such results can be obtained 
one time in ten. The rules are just as liable to make the belt 
travel 400, 1,000 or 1,600 per minute per horse-power as the 
number of feet they may give as indicating a horse-power. 

I have adopted, and all my calculations are based upon the 
assumption that a belt traveling 800 feet per minute, and running 
over pulleys, both of which are the same diameters, will easily 
transmit one horse-power for each inch in width of belt. A belt 
under such circumstances would have 180 degrees of contact on 
both pulleys without the interposition of idlers or tighteners. 

The last proposition being accepted as true and the basis cor- 
rect, the whole matter resolves itself into a very simple problem, 
so far as a belt with 180 degrees contact is concerned. It is 
simply this; If a belt traveling 800 feet per minute transmit one 
horse-power, at 1,600 feet, it will transmit two horse-power ; or 
if 2,400 feet, three horse-power, and so on. It is no trouble for 
any one to understand that, if he understands simple multiplica- 
tion or division. 

It is not, however, always the case that both pulleys are the 
same size, and as soon as the relative sizes of the pulleys change, 
the transmitting power of the belt changes ; and that is the rea- 
son why no general rule has ever, or ever will be made for ascer- 
taining the transmitting capacity of belts under all circumstances. 
When the pulleys differ in size, the larger of the two is lost sight 
of — it no longer figures in the calculations — the small pulley, 
only, must be considered. To get at it, the number of degrees 
of belt contact on the small pulley must be ascertained as nearly 
as possible and use for a guide, for getting at the transmitting 
power, the next established basis below. Of course, the experi- 
menter can make a rule for every degree of variation, but it would 
require a great many, and is not necessary. I use five divisions, 
as follows : — 



HANDBOOK ON ENGINEERING. 795 

For 180 degrees useful effect .... 100 

For 1571 " " " 92 

For 135 " " " 84 

For 112i " " " 76 

For 90 " " " 64 

The experimenters may find that my figures are under obtained 
results, which is exactly what they are intended to be, more 
especially at the 90 degree basis. I wish to make ample allow- 
ance. 

To ascertain the power a belt will transmit under the first-named 
conditions : Divide the speed of the belt in feet per minute by 
800, multiply by its width in inches and by 100. For the second, 
divide by 800, multipl}'^ by width in inches and by .92. Third 
place, divide by 800, multiply by width in inches and by .84. 
Fourth place, divide by 800, multiply by width in inches and by 
.76. Fifth place, divide by 800, multiply by width in inches and 
by .64. As an example: What would be the transmitting power 
of a 16-inch belt traveling 2,500 feet per minute by each of the 
above rules ? 

1st: 2,500 divided by 800 equal 3.125 x 16 & 100 equal 50 h. p. 
2d: 2,500 " 800 " 3.125 x 16 & .92 equal 46 " 

3d: 2,500 " 800 " 3. 125 x 16 & .84 equal 42 " 

4th: 2,500 " 800 " 3.125 x 16 & .76 equal 38 " 

5th: 2,500 " 800 " 3.125 x 16 & .64 equal 32 " 

As I have said, if the degrees of contact come between the 
divisions named above, in order to be on the safe side, calculate 
from the first rule below it, or make an approximate as you like. 

If the above lesson is studied well and strictly used, there can 
be no excuse for any mechanic puttijig in a belt too small for the 
work it has to do, provided he knows how much there is to do, 
which he ought, somewhere near at least. 



796 



HANDBOOK ON ENGINEERING. 



HORSE-POWER TRANSMITTED BY LEATHER 
BELTS. 

DRIVING POWER OF SINGLE BELTS. 



Speed in 






Width of 


Belt in Inches. 






Feet per 






































Minute. 


2 


3 


4 





6 


« 


10 


12 


14 




H. P. 


H. P. 


H. P. 


H. P. 


H. P. 


H. P. 


H. P. 


H. P 


H. P. 


400 


1 


u 


2 


2\ 


3 


4 


5 


6 


7 


600 


H 


2i 


3 


3| 


H 


6 


7^ 


9 


101 


800 


2 


3 


4 


5 


6 


8 


10 


12 


14 


1,000 


2h 


3:^ 


5 


H 


7* 


10 


m 


15 


m 


1,200 


3 


H 

5| 


7 


n 


9 


12 


15 


18 


21 


1,500 


H 


n 


9^ 


IH 


15 


18$ 


221 


261 


1 800 


H 


n 


9 


Hi 


13i 


18 


221 


27 


311 


2,000 


5 


n 


10 


12^ 


15 


20 


25 


30 


35 


2,400 


6 


9 


12 


15 


18 


24 - 


30 


36 


42 


2,800 


/ 


}:| 


14 


in 


21 


28 


35 


42 


49 


3,000 


H 


15 


18| 


22h 


30 


m 


45 


52| 


3,500 


8| 


13 


in 


22 


26 


35 


44 


521 


61 


4,000 


10 


15 


20 


25 


30 


40 


50 


60 


70 


4,500 


lU 


17 


22| 


28 


34 


45 


57 


69 


78 


5,000 


12i 


19 


25 


31 


371 


50 


621 


75 


87 



For Driving Power of Shultz Belting, add 33 per cent. 



DRIVING POWER OP DOUBLE BELTS. 



Speed in 






Width Of 


Belts in Inches. 






Feet per 




































Minute. 


6 


8 


10 


12 


14 


16 


18 


20 


24 




H. P. 


H. P. 


H. P. 


H. P 


H. p. 


H. p. 


H. P. 


H. P 


H. P. 


400 


4i 


51 


7i 


8h 


10 


lU 


13 


u* 


17* 


600 


61 


81 


11 


13 


15 


17* 


19* 


22 


26 


800 


81 


lU 


I4i 


17* 


20* 


23 


26 


29 


34* 


1,000 


11 


14^ 


184 


2U 


25* 


29 


32* 


36 


43* 


1,200 


13 


in 


22 


26 


30* 


34* 


39 


44 


52* 


1,600 


16i 


211 


27i 


32* 


38 


43* 


49 


54* 


65* 


1,800 


191 


26 


321 


39 


454 


52 


59 


65* 


78* 


2,000 


211 


29 


361 


43^1 


50* 


58 


65* 


72* 


87 


2,400 


26 


345 


44 


62* 


60* 


69* 


78* 


88 


105 


2 800 


301 


401 


51 


61 


71 


81 


91* 


102 


122 


- 3,000 


321 


431 


541 


65* 


76 


87* 


98 


108 


131 


3,500 


38 


501 


63* 


76 


89 


101 


114 


127 


153 


4,000 


431 


6&i 


721 


87 


101 


116 


131 


145 


174 


4,500 


49 


65 


82 


98 


114 


131 


147 


163 


196 


5,000 


541 


72| 


91 


109 


127 


145 


163 


182 


218 



For Driving Power of Shultz Double Belting, add 33 per cent. 



HANDBOOK ON ENGINEERING. 797 

Example. — Required the width of a single belt, the velocity of 
which is to be 1,500 feet per minute ; it has to transmit 10 horse- 
power, the diameter of the smaller drum being four feet with five 
feet of its circumference in contact with the belt. 

33,000 X 10 equal 330,000, divided by 1,500 equal 220, divided 
by 5 equal 44, divided by 6 equal 1\ inches, the required width of 
belt. 

Directions for calculating the number of horse power which a 
belt will transmit. Divide the number of square inches of belt in 
contact with the pulley by two ; multiply this quotient by the 
velocity of the belt in feet per minute ; again we divide the total 
by 33,000 and the quotient is the mumber of horse-power. 

Explanatio7is. — The early division by two is to obtain the 
number of pounds raised one foot high per minute, half a pound 
being allowed to each square inch of belting in contact with the 
pulley. 

ExamiJle. — A six-inch single belt is being moved with a 
velocity of 1,200 feet per minute, with four feet of its length in 
contact with a three-foot drum. Required the horse-power. 

6x48 equal 288, divided by 2 equal 144 x 1,200 equal 172,- 
800, divided by 33,000 equal, say, SJ horse-power. 

It is safe to reckon that a double belt will do half as much 
work again as a single one. 

Hints to users of belts. — 1. Horizontal, incHned and long- 
belts give a much better effect than vertical and short belts. 

2. Short belts require to be tighter than long ones. A long 
belt working horizontally increases the grip by its own weight. 

3. If there is too great a distance between the pulleys, the 
weight of the belt will produce a heavy sag, drawing so hard on 
the shaft as to cause great friction at the bearings ; while, at the 
same time, the belt will have an unsteady motion, injurious to 
itself and to the machinery. 

4. Care should be taken to let the belts run free and easv, so 



798 HANDBOOK ON ENGINEERING. 

as to prevent the tearing out of the lace holes at the lap ; it also 
prevents the rapid wear of the metal bearings. 

5. It is asserted that the grain side of a belt put next to the 
pulley will drive 30 per cent more than the flesh side. 

6. To obtain a greater amount of power from the belts the pul- 
leys may be covered with leather ; this will allow the belts to run 
very slack and give 25 per cent more durability. 

7. Leather belts should be well protected against water and even 
loose steam and other moisture. 

8. In putting on a belt, be sure that the joints run with the 
pulleys, and not against them out. 

9. In punching a belt for lacing, it is desirable to use an oval 
punch, the larger diameter of the punch being parallel with the 
belt, so as to cut out as little of the effective section of the leather 
as possible. 

10. Begin to lace in the center of the belt and take care to keep 
the ends exactly in line and to lace both sides with equal tight- 
ness. The lacing should not be crossed on the side of the belt that 
runs next the pulley. Thin but strong laces only should be used. 

11. It is desirable to locate the shafting and machinery so that 
belts shall run off from each other in opposite directions, as this 
arrangement will relieve the bearings from the friction that would 
result where the belts all pull one way on the shaft. 

12. If possible, the machinery should be so planned that the 
direction of the belt motion shall be from the top of the driving to 
the top of the driven pulley. 

13. Never overload a belt. 

14. A careful attention will make a belt last many years, which 
through neglect might not last one. 

DIRECTIONS FOR ADJUSTING BELTING. 

In lacing cut the ends perfectly square, else the belt will 
stretch unevenly. Make two rows of holes in each end ; put the 



HANDBOOK ON ENGINEERING. 799 

ends together and lace with lace leather, as shown in the cuts 
below. For wide belts, in addition, put a thin piece of leather or 




rubber on the back to strengthen the joint, equal in length to the 
width of the belt, and sew or rivet it to the belt. In putting on 
belting, it should be stretched as tight as possible, and with wide 
belts, this can be done best by the use of belt clamps. 

HORSE POWER OF BELTING. 

To ascertain horse-power which belts will transmit, multiply 
width of belt by diameter of pulley (in inches), by revolutions 
of pulley Cper minute), by number in table (corresponding to the 
pull the belt can exert per inch of width). 

Example. — 10" single horizontal belt, 36" pulley, 200 revolu- 
tions, pull taken at 50 lbs. 

10" X 36" X 200 X 0.0004 = 28.8 horse-power. 

The pulls which belts 1" wide will transmit are as follows : — 
Single horizontal belts (pulleys nearly same diameter) 50 lbs. 
Double '' " " "^" " 100 

Single vertical •'- '' " " 40 

Double " '• " '' " 60 

Single belts (large to very small pulleys) .... 10 
Double " L^ ^ a u .... 15 

Quarter twist, single belts . . , „ 25 

*' '' double '' ......... 40 



800 HANDBOOK ON ENGINEERIFC 



■ CHAPTER XXVIII. 

CAPACITY OF AIR COflPRESSORS. 

To ascertain the capacity of an air compressor in cubic feet of 
free air per minute, the common practice is to multiply the area 
of the intake cylinder by the feet of piston travel per minute. 
The free air capacity of the compressor, divided by the number 
of atmospheres, will give the volume of compressed air per 
minute. To ascertain the number of atmospheres at any given 
pressure, add 15 lbs. to the gauge pressure ; divide this sum by 
15 and the result will be the number of atmospheres. The above 
method of calculation, however, is only theoretical and these 
results are never obtained in actual practice, even with com- 
pressors of the very best design working under the most ifavor- 
able conditions obtainable. Allowances should be made for 
losses of various kinds, the principal losses being due to clear- 
ance spaces, but in machines of poor design and construction 
other losses occur through imperfect cooling, leakages past the 
piston and through the discharge valves, insufficient area and 
improper working of inlet valves, etc. The writer has seen com- 
pressors where losses through imperfections and improper working 
conditions ranged from 15 to 25 per cent, while under favorable 
conditions and with the average compressor, the loss averages 
from 8 to 12 per cent. So that to get sufficiently accurate 
results in finding capacity of the compressor, subtract 12 per 
cent from above computation, which gives nearly accurate 
figures. The following table will be found useful for quickly 
ascertaining the capacity of an air compressor, also to find the 
cubical contents of any cylinder, receiver, etc. The first colunni 



HANDBOOK ON ENGINEERING. 



801 



is the diam. of cylinder in inches. The second shows the cubical 
contents in feet, for each foot in length. 

Contents of a Cylinder in Cubic Feet for Eacii Foot 
in Length!. 



s i 


n 


a 02 

5| 


QQ 

11 


«5 


+2 

"1 


II 


QQ 

II 




00 

n 


1 


.0055 


6 


.1963 


11 


.6600 


20 


2.182 


36 


7.069 


u 


.0085 


H 


.2130 


lU 


.6903 


20^ 


2.292 


37 


7.468 


u 


.0123 


H 


.2305 


lU 


.7213 


21 


2.405 


38 


7.886 


11 


.0168 


61 


.2485 


11^ 


.7530 


21i 


2.521 


39 


8.296 


2 


.0218 


7 


.2673 


12 


.7854 


22 


2.640 


40 


8.728 


2i 


.0276 


7i 


.2868 


12^ 


.8523 


22i 


2.761 


41 


9.168 


H 


.0341 


7h 


.3068 


13 


.9218 


23 


2.885 


42 


9.620 


21 


.0413 


71 


.3275 


m 


.9940 


23i 


2.885 


43 


10.084 


3 


.0401 


8 


.3490 


14 


1.069 


24 


3.012 


44 


10.560 


3i 


.0576 


8i 


.3713 


m 


1.147 


25 


3.142 


45 


11.044 


3^ 


.0668 


sh 


.3940 


15 


1.227 


26 


3.400 


46 


11.540 


31 


.07«7 


81 


.4175 


15h 


1.310 


27 


3.687 


47 


12.048 


4 


.0873 


9 


.4418 


16 


1.396 


28 


3.976 


48 


12.566 


H 


.0985 


H 


.4668 


16^ 


1.485 


29 


4.587 






4i 


.1105 


H 


.4923 


17 


1.576 


30 


4.909 






4| 


.1231 


n 


.5185 


17i 


1.670 


31 


5.241 






5 


.1364 


10 


.5455 


18 


1.767 


32 


5.585 






5i 


.1503 


101 


.5730 


18.^ 


1.867 


33 


5.940 






H 


.1650 


10^ 


.6013 


19 


1.969 


34 


6.305 






51 


-.1803 


101 


.6303 


19.^ 


2.074 


35 


6.681 







To find the capacity of an air-cylinder, multiply the figures in 
the second column by the piston travel in feet per minute. This 
applies to double-acting air cylinders. In the case of single- 
acting air cylinders, the result should be divided by 2. 



THE McKIERMAN DRILL COMPANY'S AIR COHPRESSOR. 

The air-cylinder and water-jacket are one complete casting. 
The heads are made with hoods and provision made for cool air 
in- take. 



802 



HANDBOOK ON ENGINEERING. 



The atmosphere valves are bronze, of poppet form. There- 
fore, there is no vacuum and the cylinder fills absolutely with free 
air. The valves are closed by mechanical means. 

The discharge valves are self-acting, are made of bronze. All 
of them are free to inspection without removal or disturbance of 
other parts. 

The cooling" apparatus^ or heat-preventing device, is extremely 
effective. Water jacket completely surrounds the cylinder, water 




is forced to wash the walls and is kept in rapid motion from bot- 
tom to top, from end to end, absorbing heat rapidly. It «iiters 
the jacket at bottom, flows from end to end, around partitions, 
back and forth and up. Follows natural laws in absorbing, 
retaining and dispelling the heat of air. 

Regfulation of pressure and speed is entirely automatic. The 
regulating device is the only one by which the air weighs the 
steam admitted to the cylinder. Throttle may be thrown wide 
open at start, then the regulator takes absolute control, governing 
the speed from highest to lowest rate, varying the speed for 



HANDBOOK ON ENGINEERING. 



803 



variable amounts of air which may be required and in such man- 
ner as to keep the pressure constant. 




The Bennett Automatic Air Compressor. 




lugersoll-Sergeant Air Compressor. 



804 HANDBOOK ON ENGINEERING. 

INQERSOLL=SERQEANT AIR COMPRESSOR 

This engine, a cut of which is shown above, is fitted with m- 
gersoU-Sergeant Air Compressor Cylinders, and in connection 
with the Pohle Air Lift System, has double the supply of water, 
using only one-half the fuel previously required. The steam 
cylinders are of the Duplex Corliss condensing type and con- 
necting tandem, and on each side are two Ingersoll-Sergeant Air 
Cylinders and two Conover Water Cylinders. When the engine 



SECTIONAL VIEW OF AIR CYLINDER WITH VERTICAL LIFT VALVES. USED 

CLASS •■E" AND "F" COMPRESSORS. 



is in operation, the air cylinders raise the water by the Pohle Air 
Lift System, from the wells to a tank at the surface, and from 
there it is taken by the water cylinders and forced to the stand- 
pipe. The cost of this combination compares favorably with the 
old plan of using separate compressors and water pumps, each 
with their own steam cylinders, and the saving in attendance, 
friction and foundation commends its use. The engines run at a 
fixed moderate speed and the regulation of the air and water is 
effected by passing the water from suction to discharge when the 
tank is too low and by mechanically unloading the air cylinders 



HANDBOOK ON ENGINEERING. 805 

with a pressure regulator when the tank is too full. The regula- 
tion is done mechanically, with floats at the top and bottom of the 
'•eceiving tank. This combination can also be furnished with 
Straight Line Compressors ; the advantage of the Duplex is that 
should it be necessary, the one side of the engine can be discon- 
nected and the other side made to do the work. 

As will be seen, the inlet valves which are on the lower side of 
the cylinder are offset, thus preventing their being sucked into 
the cylinder and wrecking the compressor. They are made out 
of a solid piece of steel and are extremely durable, because they 
are placed vertically, work in a bath of oil and do not slide on 
their seats. Both the inlet and discharge valves, being in 
the cylinder, allow the heads to be thoroughly water-jacketed, 
and this is an important feature when it is remembered that 
the heat of compression is greatest at the end of the stroke. 
The cylinder is, therefore, completely water-jacketed. The 
valves are arranged so that the air can be taken from outside of 
the engine room, which increases the efficiency of the machine 8 
to 15 per cent, and are easily accessible. • 

The two inlet valves are located in the piston, and, with 
the tube, are carried back and forth with the piston. The valve 
on that face of the piston which is toward the direction of move- 
ment is closed, while the one on the other face is open. This is 
exactly as it should be in order to force out the compressed air 
from one end of the cylinder while taking in the free air at the 
other ; when the piston has reached the end of its travel there is, 
of course, a complete stop while the engine is passing the center, 
and an immediate start in the other direction. The valve which 
was open immediately closes , There is no reason for its remain- 
ing open any longer, and it closes at exactly the right time, its 
own weight being all that is necessary to move it. The valve 
on the other side is left behind by the piston and the free air 
18 admitted to that end of the cylinder for compression on the 



80(> 



HANDBOOK ON ENGINEERING. 



return stroke. No springs are used, and there is none of the 
throttling of the incoming air, and none of the clattering or 
hammering so noticeable with poppet-valves. As there is nothing 
to make the valve move faster than the piston, it stays behind until 
the piston stops, leaving the port wide open for the admission 




DETAILS OF PISTON INLET AIR CYLINDER. 

A.— Circulating Water Inlet. D.— Oil Hole for Automatic Oil Cup. G.— Piston Inlet Valv ' 
B.-Circulating Water Outlet. E.-Air Inlet (through piston inlet pipe). H.-Discharge Valva 
C— Water jacket Drain Pipe. F.— Air Discharge (showing flange). J.— Water Jacket. 

Sectional Cnt of Ingersoll & Sargeant Single Compressor. 



of air. It is well known that while the fly-wheel and, of course, 
the crank, rotate at a uniform speed, the movement of the piston 
is not uniform, but gradually increases in speed from the start 
till the crank has reached half -stroke, when it gradually slows up 
till the crank is on the center, and at this moment of full stop 
the valve gently slides to its seat. 



HANDBOOK ON ENGINEERIN( 

N91. ^ ^ =^ 



807 





^^^* 



J^^J. "^J^S^, fli" 




The above is what is called the Pohle Air Lift 

System, 



808 HANDBOOK ON ENGINEERING. 

The illustrations on page 807 shows the method of pumping 
water by air. A compressor in connection with the air-lift sys- 
tem of pumping water by direct air pressure. The pump con- 
sists of a water pipe and an air pipe, the latter discharging the 
air into the former at its bottom, through a specially designed 
foot-piece. The natural levity of the air compared with the 
water, causes it to rise and, in rising, to carry the water with it 
in the form of successive pistons, following one another. This 
system of pumping has found a large range of application and is 
of jjeculiar service in connection with deep well pumping. For 
this purpose, the absence of mechanical parts many feet below 
the surface, offers a commanding advantage. Method No. 1 and 
No. 2 is almost alike, consisting of placing the air and water 
pijoes alongside of one another in the well, connecting them at 
the bottom with an end piece. Method No. 3 consists of placing 
a water discharge pipe into the well ; the air passing down into 
the well through the annular space between the well casing and 
the water pipe. Method No. 4 consists in using the well casing 
as the water discharge pipe, and simply putting an air pipe down 
into the well, with a specially designed foot-piece attached at the 
bottom through which the air escapes. 



HANDBOOK ON ENGINEERING. 809 

CHAPTER XXVIII. 
THE METRIC SYSTEM. 

It frequently happens that an engineer, in reading books and 
papers devoted to steam engineering, is confronted with terms 
taken from the metric system, which he does not understand. 
I give below a few of the metric system terms most commonly 
used, with their values in feet and inches, also, gallons, quarts, 
pounds, tons, etc. 

A French meter is 30.37079 inches long, or a little less than 
39| inches. It is generally taken, — for convenience in fig- 
uring, — at 39.37 inches. 

1 decimeter is J^ of a meter, or, 3.937 inches nearly. 

1 centimeter is yJq- " " " .3937 " " 

1 millimeter is j-Jg^Q- " " " .03937 " " 



1 decameter equals 10 meters, or, 32.80 feet nearly. 
1 hectometer " 100 " " 328 " " 

1 kilometer " 1000 " " 3280 " 

APPLICATION. 

1. An engine shaft is 5 meters long, what is its length in feet 
and inches? Ans. 16 ft. 4J ins. nearly. 

Operation : ^^1^^^^^ = 16.4 ft. nearly. 

2. An engine cylinder is 10.3 decimeters in diameter, how 
much is this in inches? Ans. 40|- ins. nearly. 

Operation J 3.937 X 10.3 = 40.55 ins. nearly. 



810 HANDBOOK ON ENGINEERING. 

3. A piston-rod is ,8.7 centimeters in diameter, how much is 
this in inches? Ans. 3| ins. nearly. 

Operation ; .3937 X 8.7 = 3.42 ins. nearly. 

4. A chimney is 5.1 decameters tall, how much is this in feet 
and inches? Ans. 167 ft. 3 ins. nearly. 

Operation : 32.80 X 5.1 ^ 167.28 ft. 

5. How many miles are there in 30.2 kilometers? 

Ans. 18j7^ miles nearly. 
Operation : There are 5280 ft. in a mile. 

^, 3280 X 30.2 ,^ ^ .-, 

Then, i-^ = 18.7 miles. 

5280 

6. A valve has 2 miUimeters lead, how much is this in frac- 
tional parts of an inch? Ans. -^-^ in. nearly. 

Operation: .03937 X 2 =. .07874. 
And, .07874 X 64 = e5_. nearly. 

7. How many square feet in a circle whose diameter is one 
meter? Ans. 8^ nearly. 

^ ^. 39.37 X 39.37 X .7854 ^^^ 

Operation j -— = 8.45. 

144 

8. The cylinder clearance is 1.1 cubic decimeter, how many 
cubic inches in the clearance ? Ans. 67 nearly. 

Operation: 3.937 X 3.937 X 3.937 X 1.1 = 67.12 + 



1 gramme equals 15.433 grains, or 1 ounce nearly. 
1 kilogramme equals 2.2047 pounds avoirdupois. 
I tonne equals 1.1024 tons of 2000 lbs. 



1 litre equals 1.0566 quarts. 



HANDBOOK ON ENGINEERING. 811 



CONSEQUENTLY. 

1 U. S. gallon equal s 3.79 litres nearly. 
1 U. S. pint equals .4732 litres nearly. 

1. A main shaft weighs 800 kilogrammes, how much is this in 
avoirdupois pounds ? Ans. 1763 J lbs. nearly. 

Operation : 2.2047 X 800 = 1763.76. 

2. An engine weighs 12 tonnes, how much is this in U. S. tons 
of 2000 lbs. each? Ans. 13i tons nearly. 

Operation: 1.1024 X 12 = 13.2288. 

3 A tank contains 9000 litres of water, how much is this in 
U. S. gallons? Ans. 2377.35 galls. 

1.0566 X 9000 
Operation: t~ Because 4 quarts equal 1 gallon. 



THERMOMETERS. 

In the U* S^ tlie Fahrenheit scale is the one in most common 
use, although in our laboratories and for scientific purposes it is 
displaced by the Reaumer and Centigrade scales. Fahrenheit's 
scale marks the boiling point by 212 degrees, and the freezing 
point by 32 degrees above zero. 

The Reaumer scale marks the boiling point by 80 degrees, and 
the freezing point by zero. 

The Centigrade^ or Celsius scale, marks the boiling point b}^ 
100 degrees, and the freezing point by zero. So that, reckoning 
from the freezing point of Fahrenheit, 180 degrees Fah. equal 
80 degrees Reaumer, and 100 degrees Centigrade. Bearing in 
mind that Fahrenheit's zero is 32 degrees below the freezing point, 
one scale may readily be converted into another. 

To convert degs. of Reaumer into those of Fah. 

Rule. — Multiply by 9, divide by 4, and add 32. 



812 HANDBOOK ON ENGINEERING. 

Example: 80 degs. Reaumer equals how many clegs. Fah? 

Ans. 212. 
Operation: 80X9 = 720. 

720 
And, — - 3= 180. Then, 180 + 32 = 212. 

To convert the degs. of Centigrade into those of Fahrenheit. 
Rule* — Multiply by 9, divide by 5, and add 32. 
Example: 100 degs. Centigrade equal how many degs. Fah.? 

Ans. 212. 
Operation: 100X9 = 900. . 

A A 900 ,^^ 

And, __==180. 

5 

Then, 180+ 32=212. 

So, also, 3 degs. Centigrade equal 37.2 degs. Fahrenheit, 

Thus: 3X9=27. And, ^ =5.2. Then, 5.2 + 32 =37.2. 



ROPE TRANSMISSION. 

There are two systems of rope transmission, the English, 
or multiple-rope system, and the American or continuous wound 
rope system in which the necessary adhesion of rope to sheave is 
obtained by a tension carriage. I will treat of the American sys- 
tem only, as it is almost universally used in this country to the 
exclusion of the other. One of the most common mistakes is to 
lead the rope to the tension carriage from the tight or pulling 
side of the drive, and putting on an abnormal amount of tension 
weight in a vain endeavor to take out the slack. Under the enor- 
mous strain of such an arrangement the rope wears out very rap- 
idly, and more frequently parts at the splice. It is desirable in 
all cases of rope transmission to so arrange the drive that the 
slack side of the rope shall be on the upper part of the pulley 



HANDBOOK ON ENGINEERING. 



813 



thus increasing the arc of contact, as the two sides will then 
approach each other when in motion. The working strain in 
pounds on a rope should not exceed 200 times the square of the 
diameter of the rope. The speed of the rope should not exceed 
6500 feet per minute, and this speed gives the best results in 
H. P. The practical limit to the number of ropes for one sheave 
cannot be definitely named. The only limiting condition is the 
ability of the tension carriage to keep up the slack and when the 
number of ropes exceeds the capacity of one carriage, a second 
may be added and the drive made double. Diameters of sheaves 
should not be less than 40 diameters of the rope, and 50 to 60 
diameters are advisable, being justified by greater length of life 
of the rope. 

HORSE POWER TRANSHITTED BY ROPES. 

The following table gives the horse-power transmitted by a 
single manila rope when the arc of contact is not less than 165 
degrees, and the tension not greater than 200 times the square of 
the diameter of the rope. 



Veloc 
of Rop 


ity 

ein 




Diameter of Rope. 






Feet I 
Minu1 


)er 

te. ^/s" 


3/4" 


1" 


H" 


U" 


11" 


2" 


1000. 


1.24 


2.25 


3.57 


5.59 


8.02 


10.85 


14.20 


2000 . 


2.70 


3.84 


6.84 


10.68 


15.39 


20.93 


27.36 


2500 . 


3.30 


4.71 


8.38 


13.10 


18.86 


25.66 


33.54 


3000. 


3.83 


5.46 


9.80 


15.39 


21.87 


29.74 


38.88 


3500. 


4.30 


6.23 


11.09 


17.33 


24.94 


34.03 


44.35 


4000. 


4.74 


6.83 


12.15 


18.98 


27.33 


37.17 


48.59 


4500 . 


5.01 


7.24 


12.89 


20.15 


29.00 


39.45 


51.57 


5000 . 


5.20 


7.47 


13.29 


20.76 


29.89 


40.65 


53.15 


5500 . 


5.29 


7.60 


13.53 


21.14 


30.43 


41.39 


54.11 


6000 . 


5.08 


7.32 


13.10 


20.36 


29.32 


39.77 


52.12 


6500. 


4.74 


6.83 


12.13 


19.00 


27.34 


37.21 


48.63 


7000. 


4.12 


5.93 


10.54 


16.47 


23.72 


32.26 


42.18 


7500. 


3.25 


4.67 


8.32 


13.00 


18.73 


25.42 


33.23 



814 



HANDBOOK ON ENGINEERING. 



TO TEST THE PURITY OF ROPE. 

A simple test for the purity of manila or sisal rope is as fol- 
lows : — 

Take some of the loose fiber and roll it into balls and burn 
them completely to ashes, and, if the rope is pure manila, the ash 
will be a dull grayish black. If the rope be made from sisal the 
ash will be a whitish gray, and if the rope is made from a com- 
bination of manila and sisal the ash will be of a mixed color.. 



WIRE ROPE DATA. 

FURNISHED BY A. LESCHEN & SONS ROPE CO., ST. LOUIS, MO. 



HOISTING ROPE. 





PATENT 


FLATTENED STRAND. 




HERCU- 


CRUGI- 


IRON. 


m 


LKS. 


BLB. 








^ 00 




OB 


O 


I . 


o 


l^ 


3| 


=2.- 


^% 


5.5 


^% 


M 


M^ 


ir^o 


Jn Q 


^.as 


^^ 


bcSo 


ft 


1.2 


2^ o 


11 


III 

2^o 


ll 


Ifi 


aJ 


03 ■" 


laJ 


CQ^ 


2-1 


CQ *" 


\ 


191 


13.5 


IH 


9 


J?f 


4 


1 


2Ri^ 


22,5 


m 


15 


6 




85 


32 


24 


21 


21 


9 


1 


45 


40.5 


30 


29 


26 


13 ! 


1 


56i 


56 


39^ 


38 


34 


17 


u 


68 


67 


50 


47 


43 


21 


li 


82 


84 


59J^ 


56 


52 


28 




128 


124 


86 


81 


74 


40 




173 


168 


121 


109 


104 


54 


2 


•W2 


211 


144 


140 


120 


66 


2i 


257 


260 


182 


176 


152 


75 



19 


WIRE ROUND STRAND. 




HKRCU- 
LE8. 


CKUCI- 
j BLE. 


IRON. 


O 


§ . 


o 


s . 


- 


a . 


o 












O M 




"H 03 




■M O) 






•*^.o 


5 


II 

u 


bc2S 

III 

2-J3 o 




O O 




a o 

Hi 


CLi 


CO «= 


£ 


ca "" 


&J 


CQ •" 




Uh 


12.5 


11 


8.8 


8 


4 




m 


20 


14 


13 6 


12 


6 




30 


29 


18 


19.4 


16 


9 




39 


36 


23 


26 


20 


13 




48^ 


50 


30 


34 


26 


17 


1 


57^ 


60 


38 


42 


33 


21 




71 


77 


46 


50 


40 


25 




103 


113 


66 


72 


57 


36 




147 


157 


93 


96 


80 


48 


2 


172 


191 


111 


124 


92 


62 


2J 


218 


238 


142 


1.^6 


117 


74 



INDEX. 

The elementary principles of electrical machinery, 1. 

A permanent magnet, 1 to 2. 

Two-bar magnet, 3 to 6. 

A magnet needle, 3. 

Magnetic lines of force, 6. . 

Lines of force, 6 to 14. 

Magnetic force, 13. 

To find the lifting capacity of a magnet, 13. 

The principles of electromagnetic induction, 14 to 22. 

The armature cores, 23 to 27. 

The simplest type of armature winding, 27 to 29. 

Two-pole generators and motors, 27 to 30. 

The general arrangement of the field and armature in a two-pole 
machine, 31 to 33. 

The reason why brushes are set differently on motors than on 
dynamos, 36 to 37. 

Multipolar machines, 38 to 39. 

Setting the brushes on a four-pole machine, 40. 

Setting the brushes on an eight-pole machine, 41. 

The lap and wave winding for four-pole machine, 42 to 46. 

Switch-boards, distributing circuits and switch-board instru- 
ments, 47. 

Generators of the constant potential, 47 to 48. 

The switch-board arranged for two generators of the shunt type, 
49 to 61„ 

Switch-board for three- wire system, 56 to 57. 

To wire a large building with a lighting and power system, 58 
to GO. 

(815) 



816 INDEX. 

The ammeters, 61. 

Circuit breakers, 62 to 63. 

The electromotive in volts force, etc., 63. 

Electric motors, 64. 

Motors and their connections, 64 to 73. 

The strength of an electric current, etc., 73. 

The watt, 73. 

The ampere, 73. 

Candle power, 73. 

Instructions for installing and operating slow and moderate speed 
generators and motors, 74 to 85. 

Brush setting, 75 to 78, 

Before starting a dynamo, 78. 

Care of commutators, 78 to 79. 

Directions for starting dynamos, 79 to 81. 

Switching dynamos into circuit, 82. 

Dynamos in parallel, 82 to 83. 

Directions for running dynamos and motors, 83 to 84. 

Personal safety, 85. 

Why commutator brushes spark and why they do not spark, 80 
to 101. 

Heating in dynamo, or motor, 101 to 103. 

The effect of the displacement of the armature, 103 to 110. 

Noise in dynamos, 110 to 112. 

Table of carrying capacity of wires, 113 to 116. 

Instructions for installing and operating apparatus for arc light- 
ing Brush system, 117 to 167. 

Table showing the relative resistance of metals at temperature of 
70 degrees Fah., 167. 

The Thomson-Houston system, 168 to 209. 

Table of magnetizing force in ampere turns required, etc., 209. 

The selection of an engine, 210. 

The gain by expansion, 216. 



IXDKX. 817 

Table of cut-off iu j^arts of the stroke, 21(S, 

The steam engme governor, 216 and 226. 

The fly-wheel, 217. 

Horse power, 218. 

Care and management of a steam engine, 218. 

Lubrication of an engine, 219. 

Selecting an oil for an engine, 220. 

The piston packing, 220. 

Crank-pins, 221. 

Connecting rod brasses, 222. 

Knocking in engines, 222, 223. 

The main bearings, 223, 225, 

Repairs of engines, 224. 

Fitting a slide valve, 224. 

Eccentric straps, 225. 

Heating of journals, 226. 

Automatic engines, 227. 

To find the dead centers, 228. 

View of tandem compound engine and its foundation, 231. 

How to line an engine, 232, 236. 

How to pipe a twin tandem compound engine, 233. 

What is work, 237. 

What is power, 237. 

Horse-power of an engine, 238. 

General proportions of engines, 238. 

Rules for weights of fly-wheels, 239. 

View of the Russell engine, 240-244. 

Setting the valves of Russell engines, 240-244. 

View of horizontal Corliss engine, 250. 

Directions for setting up, adjusting and running Corliss engines, 

251-253. 
The steam engine condenser, 255-257. 
Vacuum in condenser, 256. 



818 INDEX. 

Amount of condensing water required, 256. 

Corliss engine regulation, 257. 

View of the Porter- Allen engine, 258. 

Description of the Porter- Allen engine, 259, 271. 

Directions for setting the valves, and running the Porter- Allen 

engine, 271, 273. 
Specifications for centrally balanced Centrifugal Inertia Governor, 

273, 275. 
The Armington and Sims engine, 275. 
Setting the valve in an Armington and Sims engine, 275. 
The Harrisburg engine, 276. 

The care and management of the Harrisburg engine, 276, 281. 
The Mcintosh and Seymour High Speed engine, 281. 
How to set the valves of a M. & S. engine, 282. 
The Ideal engine, 283. 

Instructions for starting and operating Ideal engines, 283, 2iU. 
Instructions for indicating Ideal engines, 291, 292. 
The Westinghouse Compound engine, 293. 
Instructions for starting and operating a Westinghouse Compound 

engine, 293, 309. 
How to set the main valve on a Westinghouse engine, 301. 
Some points on cylinder lubrication, 309. 
Automatic lubricators, 310, 312. 
Setting a plain slide valve with link motion, 313, 318, 
Valve setting for engineers, 318, 322. 
View of a slide valve engine showing the point of taking steam, 

321. 
View of a slide valve engine showing the point of cut-off, 321. 
View showing the position of the valve when compression begins, 

321, 322. 
Taking charge of a steam power plant, 323, 326. 
Economy in steam power plants, 327, 329. 
Priming in boilers, 329. 



INDEX. 819 

Condensing engines, 329, 331. 

High pressure steam, 332, 335. 

Using steam full stroke, 335, 337. 

Slide valve engines, 337. 

Regular expansion engines, 338. 

Automatic cut-off engines, 339, 340. 

The Gardiner spring governor, 341, 344. 

The Gardiner Standard Governor, 341, 344. 

A few remarks on the indicator, 345. 

The use of the indicator in setting valves, etc., 34(3. 

A card from a throttling engine, 347, 349. 

A card from an automatic engine, 350, 351. 

Calculating mean effective pressure, 339, 353. 

The theoretical curve, 353, 357. 

A card from a Corliss engine, 357. 

A stroke card, 358. 

A steam chest card, 359. 

Eccentric out of place cards, 360, 361. 

Eccentric cards, 361, 365. 

How to take an indicator diagram, 365, 370. 

Cards from " Eclipse " ice machine plant, 371, 373. 

A collection of diagrams which illustrate very nicely the peculiar- 
ities and difference in the action of threttling and automatic 
engines, 374, 379. 

The question whether or not more steam is used when an engine 
is made to run faster without changing either the cut-off or 
the pressure, 380. 

How to increase the power of a Corliss engine, 381, 382. 

How to increase the power of an engine having a throttling gov- 
ernor, 383. 

How to increase the horse power of an engine having a shaft 
governor, 385. 

How to line an engine with a shaft Dlaced at a higher or a lower 
level, 385, 387. 



820 INDEX. 

How to line the engine with a shaft to which it is to be coupled 

direct, 387. 
HoAV to set a slide valve in a hurry, 388. 
A few things for an engineer to remember, 388. 
The travel of a slide valve, 390. 
Loss of heat from uncovered steam pipes, 391. 
Rules and problems appertaining to the steam engine, 392, 395. 
To find the water consumption of a steam engine, 395, 397. 
Table of hyperbolic logarithms, 397. 
The force of steam and where it comes from, 398, 400. 
The energy stored in steam boilers, 400, 401. 
Standard high pressure boilers, 401. 
Types of boilers, 402. 
Horse power of boilers, 402, 404. 
The rating of boilers, 404. 
Working capacity of boilers, 405, 406. 
Code of rules for making boiler tests, 407, 414. 
Definitions as applied to boilers and boiler material, 415. 
Heat and steam, 416, 421. 
Selection of a boiler, 422, 425. 
Boiler trimmings, 426, 432. 
The care and management of a boiler, 433, 437. 
Water for use in boilers, 438, 448. 
The use and abuse of the steam boiler, 449, 453. 
Design of steam boilers, 454, 455. 
Forms of steam boilers, 456. 
Setting steam boilers, 456, 457. 

Defects in the construction of steam boilers, 457, 459, 
Improvements in steam boilers, 459, 461. 
Strength of riveted seams, 461, 466. 
Maximum pitches for riveted lap joints, 466. 
Iron plates and iron rivets, double riveted lap joints, 467. 
Zitrzap' rivetinof and chain rivetino;, 468, 472. 



821 



Single riveted lap joints, iron plates, 4(30. 

Steel plates and steel rivets, S. R. L. J., 470, 

Steel plates and steel rivets, D. R. L. J., 471. 

Strength of stayed flat boiler surfaces, 473. 

Boiler stays, 474, 477. 

Riveted and lap welded flues, 477, 481. 

Table of allowable steam pressure on flues, 478, 479. 

Thickness of material required for tubes, 481, 486. 

Table of wrought-iron welded pipe, 486. 

Pulsation in steam boilers, 487, 488. 

Weight of square and round iron per lineal foot, 488. 

Water columns for boilers, 489. 

Steam gauges, 489, 490. 

Safety valves, 491, 499. 

Table of the rise of safety valves, 495. 

Safety valve rules, 497. 

Table of heating surf ace in square feet, 501. 

Centrifugal force, 501. 

The water tube sectional boiler, 502, 508. 

The down draft furnace, 503, 522. 

View of boiler setting and furnace common in the east, 513. 

Vertical tubular boilers, 514, 521. 

Proper water column connections, 515. 

Table of pressures allowable in boilers, 516. 

Fire line in boiler settings, 520. 

Proper location of gauge cocks, 521. 

Number of bricks required for boiler setting, 522. 

Specifications for a sixty-inch 6 in. flue boiler, 524. 

Banking fires, 531. 

Instructions for boiler attendants, 532. 

Rules and problems anent steam boilers, 536. 

Steam jets for smoke prevention, 542. 

The Worthington Compound pump, 544. 



822 INDEX. 

View of steam valves projjerly set, 545. 

The Deane steam-pump, 546. 

View of steam valves properly set, 547. 

The Cameron steam pump, 548. 

Explanation of steam end, 548. 

View of steam valves properly set, 548 

The Knowles steam pump, 550. 

Explanation of steam valves, 550. 

View of steam valves pro23erly set, 552. 

The Hooker steam pump, 553. 

Operation of the Hooker pump, 553. 

View of steam valves properly set, 555. 

The Blake steam pump, 555. 

Operation of the Blake pump, 555. 

View of steam valves properly set, 558. 

Miscellaneous pump questions and answers, 559, 580-603-617. 

How to set the steam valves of a duplex pump, 567. 

View of steam valves properly set, 568. 

Proper pipe connections, 569. 

View of pipe connections, 570. 

Pumps refusing to lift water, 577. 

Corrosion in water pipes, 579. 

Pumping acids, 579. 

Selecting boiler for a steam pump, 580. 

The Worthington water meter, 581. 

Table of water pressure due to height, 582. 

Table of decimal equivalents of 16ths, 32nds and 64ths of an 

inch, 583. 
Capacity of tanks in U. S. gallons, 584. 
Capacity of square cisterns in U. S. gallons, 585. 
Weight of water, 585. 
Cost of water, 587. 
Loss by friction of water in pipes, 588. 



ixDEX. 823 

How water may be wasted, 589. 

Ignition j^oints of various substances, 589. 

Pump notes, 564. 

Steam pump rules and problems, 603, 617. 

First appearance of the injector, 592. 

G-eneral directions for piping injectors, 594. 

Care and management of injectors, 598, 602. 

Directions for connecting and operating the Hancock inspirator, 

597. 
Mechanical refrigeration — How it is produced, 619. 
Principles of operation, 620. 
Operation of apparatus, 620. 
Function of the pump and condenser, 621. 
What does the work, 621. 
Mechanical cold easily regulated, 622. 
Utilizing the cold, 622. 
Brine system, 622. 
Direct expansion system, 623. 
Rating of the machine in tons capacity, 623. 
Difference in these ratings, 623. 
Unit of capacity, 624. 
The preparation of brine, 624. 
Insulation of buildings, 626. 
Perfect insulation, 628. 
A few tests for ammonia, 629. 
Testing for water by evaporation, 629. 
Lubrication of refrigerating machinery, 630. 
Effects of ammonia on pipes, 631. 
To charge the system with ammonia, 632. 
Process of mechanical refrigeration, 633. 
View of the " Eclipse " compressor, 635. 
The compressor pumps, 636. 
The De La Vergne horizontal compressor, 636. 



824 INDEX. 

Pipe arrangement for vaults, 637. 

Diagram of the De La Vergne system, (3o8, 

Rating machines for ice making, 638. 

A complete ice making plant, 639, 641. 

View of double acting compressor, 640, 644 

A complete refrigerating plant, 642. 

Reasons why pumps do not work, 647. 

Priming in boilers, 648. 

Foaming in boilers, 648. 

In case of low water in a boiler, 649. 

Best economy in running an engine, 650. 

What is valve lead, 653, 666, 668. 

What is meant by expansion of steam, 654. 

Describe the Corliss valve gear, 654. 

What is lap on a valve, 654, 666, 670. 

Taking up lost motion in an engine, 654. 

Direct and indirect valve motion, 668. 

To test a piston for leakage of steam, 669. 

How to line up an extension to a line shaft, 672. 

Simplicity in steam piping, 674. 

Cutting pipe to order, 675. 

Feed water required for small engines,' 676. 

Heating feed water, 6 76. 

Rating boilers by feed water, 676. 

Weights of feed water and of steam, 677. 

Feed water heaters, 678. 

Table showing the units of heat required to convert one pound 
of water at the temperature of 32° Fah., into steam at dif- 
ferent pressures, 679. 

Table showing gain in use of feed water heaters, and percentage 
of heat required to heat water for different feed and boiling- 
temperatures, as compared with a feed and boiling tempera- 
ture of 212°, 680. 

Pure water, 682. ij 



INDEX. 825 

The temperature and pressure of saturated steam, 684. 

Something for nothing, 686. 

Melting points of metals, 687. 

Chimneys, 688, 694. 

Weight of steel smoke stacks per linear foot, 694. 

Horse power of gears, 696. 

Table of H. P. of shafts, 697. 

Prime movers, 697. 

Wheel gearing, 698. 

The pitch line of a gear wheel, 698. 

To find the pitch of a wheel, 698. 

To find the chordal pitch, 699, 703. 

To find the diameter of a wheel, 699, 703. 

To find the number of teeth for a wheel, 699, 705. 

To find the proportional radius of a wheel or pinion, 700. 

To find the diameter of a pinion, 700. 

To find the circumference of a wheel, 700. 

To find the number of revolutions of a wheel or pinion, 700, 701. 

Stress on gear teeth, 705. 

A train of wheels and pinions, 701. 

Table of diameters and pitches of wheels, 704. 

Curves of teeth, 705. 

Construction of gearing, 706. 

Bevel wheels, 707. 

Worm-screw, 708. 

Proportions of teeth of wheels, 709. 

To find the depth of a cast-iron tooth, 709. 

To find the horse-power of a tooth, 710. 

Calculating the speed of gears, 710. 

When time must be regarded, 711. 

Table of weight of a square foot of sheet iron, 712. 

Screw cutting, 713. 

Transmission of power by Manila rope, 714, 812, 813. 

Decimal equivalents of one foot by inches, 714. 



826 INDEX. 

Table of transmission of power by wire ropes, 715, 814. 

Electric elevators — The Otis elevator, 716. 

Belt driven elevators, 716, 725. 

Direct connected elevators, 717, 730. 

The motor-starting switch, 719. 

The elevator machine brake, 719. 

The main hand rope, 719. 

View of connections of gravity motor controller to elevator, 722. 

View of connections of gravity motor controller with separate 

rope attachment, 723. 
Automatic stops, 733. 
View of circuit connections, 734. 
The starting resistance, 735. 
The switch lever, 736. 
Cutting out the series field coils, 737. 
The safety brake magnet, 739. 
The proper care of machines, 739, 779. 
How to start the car, 743. 
The car switch, 748. 
The slack cable switch, 749. 
Electric control for private house elevators, 749, 
View of wiring for private houses, 750. 
The Sprague Electric Co.'s elevators, 756. 
View of operative circuits for Sprague screw elevator, 762. 
The pilot motor, 763. 
Care of Sprague elevators, 765. 

Directions for the care and operation of electric elevators, 766. 
Directions for the care and operation of electric elevators, 769. 
Hydraulic Elevators — How to pack hydraulic vertical cylinder 

elevators, 769. 
How to set the hand cable on a lever machine, 770. 
How to pack vertical cylinder valves, 771. 
View of Otis vertical hydraulic elevator and valve chamber, and 

packing same, 772-74. j| 



INDEX. 827 

View of the Crane auxiliary and main valve, and operation of 

same, 772, 775-76. 
Otis gravity wedge safety, 777. 
Care of Hale elevators, 777. 
Water for use in hydraulic elevators, 778-781. 
Otis differential and auxiliary valve, 780. 
Elevator inclosures and their care, 782. 
Standard hoisting rope with 19 wires to the strand, 783. 
Cables, and how to care for them, 783. 
Lubrication for hydraulic elevators, 785. 
Belts, and how to care for them, 786. 
Useful information, 786. 
To find leaks in pressure tanks, 786. 
Decimal equivalents of an inch, 787. 

The average strain or tension at which belting should be run, 788. 
Rules and problems anent belting, 788, 797. 
Extracts from articles on belts, by R. J. Abernathey, 790. 
Transmitting power of belts, 795, 
Table of horse-power of belts, 796, 799. 
Directions for adjusting belting, 798. 
Losses in air compressors, 800. 
Capacity of air compressors, 800. 

Contents of a cylinder in cubic feet for each foot in length, 801. 
The McKierman air compressor, 801. 
The Bennett automatic air compressor, 803. 
The Ingersoll-Sergeant air compressor, 803. 
The Pohle air-lift system, 807. 
The metric system, 809. 
Thermometers, 811. 
Rope transmission, 714, 812. 
Horse-power transmitted by hemp ropes, 813. 
To test the purity of hemp rope, 814. 
Wire rope data, 814. 



w^^ 



